Update imgui to 1.67. Also update imguicolortextedit.

2025-03-20 07:40:02 +08:00 · 2019-01-19 14:05:54 +01:00
parent 32f0a27d3b
commit ac791fd19f
16 changed files with 6461 additions and 3818 deletions
@@ -1,6 +1,6 @@
-// Wrapper to use Freetype (instead of stb_truetype) for Dear ImGui
+// Wrapper to use FreeType (instead of stb_truetype) for Dear ImGui
 // Get latest version at https://github.com/ocornut/imgui/tree/master/misc/freetype
-// Original code by @Vuhdo (Aleksei Skriabin). Improvements by @mikesart. Maintained by @ocornut
+// Original code by @vuhdo (Aleksei Skriabin). Improvements by @mikesart. Maintained and v0.60+ by @ocornut.

 // Changelog:
 // - v0.50: (2017/08/16) imported from https://github.com/Vuhdo/imgui_freetype into http://www.github.com/ocornut/imgui_club, updated for latest changes in ImFontAtlas, minor tweaks.
@@ -10,6 +10,7 @@
 // - v0.54: (2018/01/22) fix for addition of ImFontAtlas::TexUvscale member
 // - v0.55: (2018/02/04) moved to main imgui repository (away from http://www.github.com/ocornut/imgui_club)
 // - v0.56: (2018/06/08) added support for ImFontConfig::GlyphMinAdvanceX, GlyphMaxAdvanceX
+// - v0.60: (2019/01/10) re-factored to match big update in STB builder. fixed texture height waste. fixed redundant glyphs when merging. support for glyph padding.

 // Gamma Correct Blending:
 //  FreeType assumes blending in linear space rather than gamma space.
@@ -17,18 +18,16 @@
 //  For correct results you need to be using sRGB and convert to linear space in the pixel shader output.
 //  The default imgui styles will be impacted by this change (alpha values will need tweaking).

-// TODO:
-// - Output texture has excessive resolution (lots of vertical waste).
-// - FreeType's memory allocator is not overridden.
-// - cfg.OversampleH, OversampleV are ignored (but perhaps not so necessary with this rasterizer).
+// FIXME: FreeType's memory allocator is not overridden.
+// FIXME: cfg.OversampleH, OversampleV are not supported (but perhaps not so necessary with this rasterizer).

 #include "imgui_freetype.h"
-#include "imgui_internal.h"   // ImMin,ImMax,ImFontAtlasBuild*,
+#include "imgui_internal.h"     // ImMin,ImMax,ImFontAtlasBuild*,
 #include <stdint.h>
 #include <ft2build.h>
-#include FT_FREETYPE_H
-#include FT_GLYPH_H
-#include FT_SYNTHESIS_H
+#include FT_FREETYPE_H          // <freetype/freetype.h>
+#include FT_GLYPH_H             // <freetype/ftglyph.h>
+#include FT_SYNTHESIS_H         // <freetype/ftsynth.h>

 #ifdef _MSC_VER
 #pragma warning (disable: 4505) // unreferenced local function has been removed (stb stuff)
@@ -74,15 +73,15 @@ namespace
    /// A structure that describe a glyph.
    struct GlyphInfo 
    {
-        float Width;		// Glyph's width in pixels.
-        float Height;		// Glyph's height in pixels.
-        float OffsetX;		// The distance from the origin ("pen position") to the left of the glyph.
-        float OffsetY;		// The distance from the origin to the top of the glyph. This is usually a value < 0.
-        float AdvanceX;		// The distance from the origin to the origin of the next glyph. This is usually a value > 0.
+        int         Width;              // Glyph's width in pixels.
+        int         Height;             // Glyph's height in pixels.
+        FT_Int      OffsetX;            // The distance from the origin ("pen position") to the left of the glyph.
+        FT_Int      OffsetY;            // The distance from the origin to the top of the glyph. This is usually a value < 0.
+        float       AdvanceX;           // The distance from the origin to the origin of the next glyph. This is usually a value > 0.
    };

    // Font parameters and metrics.
-    struct FontInfo 
+    struct FontInfo
    {
        uint32_t    PixelHeight;        // Size this font was generated with.
        float       Ascender;           // The pixel extents above the baseline in pixels (typically positive).
@@ -96,82 +95,80 @@ namespace
    // NB: No ctor/dtor, explicitly call Init()/Shutdown()
    struct FreeTypeFont
    {
-        bool        Init(const ImFontConfig& cfg, unsigned int extra_user_flags);   // Initialize from an external data buffer. Doesn't copy data, and you must ensure it stays valid up to this object lifetime.
-        void        Shutdown();
-        void        SetPixelHeight(int pixel_height);                               // Change font pixel size. All following calls to RasterizeGlyph() will use this size
-
-        bool        CalcGlyphInfo(uint32_t codepoint, GlyphInfo& glyph_info, FT_Glyph& ft_glyph, FT_BitmapGlyph& ft_bitmap);
-        void        BlitGlyph(FT_BitmapGlyph ft_bitmap, uint8_t* dst, uint32_t dst_pitch, unsigned char* multiply_table = NULL);
+        bool                    InitFont(FT_Library ft_library, const ImFontConfig& cfg, unsigned int extra_user_flags); // Initialize from an external data buffer. Doesn't copy data, and you must ensure it stays valid up to this object lifetime.
+        void                    CloseFont();
+        void                    SetPixelHeight(int pixel_height); // Change font pixel size. All following calls to RasterizeGlyph() will use this size
+        const FT_Glyph_Metrics* LoadGlyph(uint32_t in_codepoint);
+        const FT_Bitmap*        RenderGlyphAndGetInfo(GlyphInfo* out_glyph_info);
+        void                    BlitGlyph(const FT_Bitmap* ft_bitmap, uint8_t* dst, uint32_t dst_pitch, unsigned char* multiply_table = NULL);
+        ~FreeTypeFont()         { CloseFont(); }

        // [Internals]
        FontInfo        Info;               // Font descriptor of the current font.
+        FT_Face         Face;
        unsigned int    UserFlags;          // = ImFontConfig::RasterizerFlags
-        FT_Library      FreetypeLibrary;
-        FT_Face         FreetypeFace;
-        FT_Int32        FreetypeLoadFlags;
+        FT_Int32        LoadFlags;
    };

    // From SDL_ttf: Handy routines for converting from fixed point
    #define FT_CEIL(X)  (((X + 63) & -64) / 64)

-    bool FreeTypeFont::Init(const ImFontConfig& cfg, unsigned int extra_user_flags)
+    bool FreeTypeFont::InitFont(FT_Library ft_library, const ImFontConfig& cfg, unsigned int extra_user_flags)
    {
        // FIXME: substitute allocator
-        FT_Error error = FT_Init_FreeType(&FreetypeLibrary);
+        FT_Error error = FT_New_Memory_Face(ft_library, (uint8_t*)cfg.FontData, (uint32_t)cfg.FontDataSize, (uint32_t)cfg.FontNo, &Face);
        if (error != 0)
            return false;
-        error = FT_New_Memory_Face(FreetypeLibrary, (uint8_t*)cfg.FontData, (uint32_t)cfg.FontDataSize, (uint32_t)cfg.FontNo, &FreetypeFace);
-        if (error != 0)
-            return false;
-        error = FT_Select_Charmap(FreetypeFace, FT_ENCODING_UNICODE);
+        error = FT_Select_Charmap(Face, FT_ENCODING_UNICODE);
        if (error != 0)
            return false;

        memset(&Info, 0, sizeof(Info));
        SetPixelHeight((uint32_t)cfg.SizePixels);

-        // Convert to freetype flags (nb: Bold and Oblique are processed separately)
+        // Convert to FreeType flags (NB: Bold and Oblique are processed separately)
        UserFlags = cfg.RasterizerFlags | extra_user_flags;
-        FreetypeLoadFlags = FT_LOAD_NO_BITMAP;
-        if (UserFlags & ImGuiFreeType::NoHinting)      FreetypeLoadFlags |= FT_LOAD_NO_HINTING;
-        if (UserFlags & ImGuiFreeType::NoAutoHint)     FreetypeLoadFlags |= FT_LOAD_NO_AUTOHINT;
-        if (UserFlags & ImGuiFreeType::ForceAutoHint)  FreetypeLoadFlags |= FT_LOAD_FORCE_AUTOHINT;
-        if (UserFlags & ImGuiFreeType::LightHinting)   
-            FreetypeLoadFlags |= FT_LOAD_TARGET_LIGHT;
-        else if (UserFlags & ImGuiFreeType::MonoHinting)   
-            FreetypeLoadFlags |= FT_LOAD_TARGET_MONO;
+        LoadFlags = FT_LOAD_NO_BITMAP;
+        if (UserFlags & ImGuiFreeType::NoHinting)
+            LoadFlags |= FT_LOAD_NO_HINTING;
+        if (UserFlags & ImGuiFreeType::NoAutoHint)
+            LoadFlags |= FT_LOAD_NO_AUTOHINT;
+        if (UserFlags & ImGuiFreeType::ForceAutoHint)
+            LoadFlags |= FT_LOAD_FORCE_AUTOHINT;
+        if (UserFlags & ImGuiFreeType::LightHinting)
+            LoadFlags |= FT_LOAD_TARGET_LIGHT;
+        else if (UserFlags & ImGuiFreeType::MonoHinting)
+            LoadFlags |= FT_LOAD_TARGET_MONO;
        else                                                
-            FreetypeLoadFlags |= FT_LOAD_TARGET_NORMAL;
+            LoadFlags |= FT_LOAD_TARGET_NORMAL;

        return true;
    }

-    void FreeTypeFont::Shutdown()
+    void FreeTypeFont::CloseFont()
    {
-        if (FreetypeFace) 
+        if (Face) 
        {
-            FT_Done_Face(FreetypeFace);
-            FreetypeFace = NULL;
-            FT_Done_FreeType(FreetypeLibrary);
-            FreetypeLibrary = NULL;
+            FT_Done_Face(Face);
+            Face = NULL;
        }
    }

    void FreeTypeFont::SetPixelHeight(int pixel_height) 
    {
-        // I'm not sure how to deal with font sizes properly.
-        // As far as I understand, currently ImGui assumes that the 'pixel_height' is a maximum height of an any given glyph,
-        // i.e. it's the sum of font's ascender and descender. Seems strange to me.
+        // Vuhdo: I'm not sure how to deal with font sizes properly. As far as I understand, currently ImGui assumes that the 'pixel_height' 
+        // is a maximum height of an any given glyph, i.e. it's the sum of font's ascender and descender. Seems strange to me.
+        // NB: FT_Set_Pixel_Sizes() doesn't seem to get us the same result.
        FT_Size_RequestRec req;
        req.type = FT_SIZE_REQUEST_TYPE_REAL_DIM;
        req.width = 0;
        req.height = (uint32_t)pixel_height * 64;
        req.horiResolution = 0;
        req.vertResolution = 0;
-        FT_Request_Size(FreetypeFace, &req);
+        FT_Request_Size(Face, &req);

-        // update font info
-        FT_Size_Metrics metrics = FreetypeFace->size->metrics;
+        // Update font info
+        FT_Size_Metrics metrics = Face->size->metrics;
        Info.PixelHeight = (uint32_t)pixel_height;
        Info.Ascender = (float)FT_CEIL(metrics.ascender);
        Info.Descender = (float)FT_CEIL(metrics.descender);
@@ -180,52 +177,58 @@ namespace
        Info.MaxAdvanceWidth = (float)FT_CEIL(metrics.max_advance);
    }

-    bool FreeTypeFont::CalcGlyphInfo(uint32_t codepoint, GlyphInfo &glyph_info, FT_Glyph& ft_glyph, FT_BitmapGlyph& ft_bitmap)
+    const FT_Glyph_Metrics* FreeTypeFont::LoadGlyph(uint32_t codepoint)
    {
-        uint32_t glyph_index = FT_Get_Char_Index(FreetypeFace, codepoint);
+        uint32_t glyph_index = FT_Get_Char_Index(Face, codepoint);
        if (glyph_index == 0)
-            return false;
-        FT_Error error = FT_Load_Glyph(FreetypeFace, glyph_index, FreetypeLoadFlags);
+            return NULL;
+        FT_Error error = FT_Load_Glyph(Face, glyph_index, LoadFlags);
        if (error)
-            return false;
+            return NULL;

        // Need an outline for this to work
-        FT_GlyphSlot slot = FreetypeFace->glyph;
+        FT_GlyphSlot slot = Face->glyph;
        IM_ASSERT(slot->format == FT_GLYPH_FORMAT_OUTLINE);

+        // Apply convenience transform (this is not picking from real "Bold"/"Italic" fonts! Merely applying FreeType helper transform. Oblique == Slanting)
        if (UserFlags & ImGuiFreeType::Bold)
            FT_GlyphSlot_Embolden(slot);
        if (UserFlags & ImGuiFreeType::Oblique)
+        {
            FT_GlyphSlot_Oblique(slot);
+            //FT_BBox bbox;
+            //FT_Outline_Get_BBox(&slot->outline, &bbox);
+            //slot->metrics.width = bbox.xMax - bbox.xMin;
+            //slot->metrics.height = bbox.yMax - bbox.yMin;
+        }

-        // Retrieve the glyph
-        error = FT_Get_Glyph(slot, &ft_glyph);
-        if (error != 0)
-            return false;
-
-        // Rasterize
-        error = FT_Glyph_To_Bitmap(&ft_glyph, FT_RENDER_MODE_NORMAL, NULL, true);
-        if (error != 0)
-            return false;
-
-        ft_bitmap = (FT_BitmapGlyph)ft_glyph;
-        glyph_info.AdvanceX = (float)FT_CEIL(slot->advance.x);
-        glyph_info.OffsetX = (float)ft_bitmap->left;
-        glyph_info.OffsetY = -(float)ft_bitmap->top;
-        glyph_info.Width = (float)ft_bitmap->bitmap.width;
-        glyph_info.Height = (float)ft_bitmap->bitmap.rows;
-
-        return true;
+        return &slot->metrics;
    }

-    void FreeTypeFont::BlitGlyph(FT_BitmapGlyph ft_bitmap, uint8_t* dst, uint32_t dst_pitch, unsigned char* multiply_table)
+    const FT_Bitmap* FreeTypeFont::RenderGlyphAndGetInfo(GlyphInfo* out_glyph_info)
+    {
+        FT_GlyphSlot slot = Face->glyph;
+        FT_Error error = FT_Render_Glyph(slot, FT_RENDER_MODE_NORMAL);
+        if (error != 0)
+            return NULL;
+
+        FT_Bitmap* ft_bitmap = &Face->glyph->bitmap;
+        out_glyph_info->Width = (int)ft_bitmap->width;
+        out_glyph_info->Height = (int)ft_bitmap->rows;
+        out_glyph_info->OffsetX = Face->glyph->bitmap_left;
+        out_glyph_info->OffsetY = -Face->glyph->bitmap_top;
+        out_glyph_info->AdvanceX = (float)FT_CEIL(slot->advance.x);
+
+        return ft_bitmap;
+    }
+
+    void FreeTypeFont::BlitGlyph(const FT_Bitmap* ft_bitmap, uint8_t* dst, uint32_t dst_pitch, unsigned char* multiply_table)
    {
        IM_ASSERT(ft_bitmap != NULL);
-
-        const uint32_t w = ft_bitmap->bitmap.width;
-        const uint32_t h = ft_bitmap->bitmap.rows;
-        const uint8_t* src = ft_bitmap->bitmap.buffer;
-        const uint32_t src_pitch = ft_bitmap->bitmap.pitch;
+        const uint32_t w = ft_bitmap->width;
+        const uint32_t h = ft_bitmap->rows;
+        const uint8_t* src = ft_bitmap->buffer;
+        const uint32_t src_pitch = ft_bitmap->pitch;

        if (multiply_table == NULL)
        {
@@ -246,143 +249,332 @@ namespace
 #define STB_RECT_PACK_IMPLEMENTATION
 #include "imstb_rectpack.h"

-bool ImGuiFreeType::BuildFontAtlas(ImFontAtlas* atlas, unsigned int extra_flags)
+struct ImFontBuildSrcGlyphFT
+{
+    GlyphInfo           Info;
+    uint32_t            Codepoint;
+    unsigned char*      BitmapData;         // Point within one of the dst_tmp_bitmap_buffers[] array
+};
+
+struct ImFontBuildSrcDataFT
+{
+    FreeTypeFont        Font;
+    stbrp_rect*         Rects;              // Rectangle to pack. We first fill in their size and the packer will give us their position.
+    const ImWchar*      SrcRanges;          // Ranges as requested by user (user is allowed to request too much, e.g. 0x0020..0xFFFF)
+    int                 DstIndex;           // Index into atlas->Fonts[] and dst_tmp_array[]
+    int                 GlyphsHighest;      // Highest requested codepoint
+    int                 GlyphsCount;        // Glyph count (excluding missing glyphs and glyphs already set by an earlier source font)
+    ImBoolVector        GlyphsSet;          // Glyph bit map (random access, 1-bit per codepoint. This will be a maximum of 8KB)
+    ImVector<ImFontBuildSrcGlyphFT>   GlyphsList;
+};
+
+// Temporary data for one destination ImFont* (multiple source fonts can be merged into one destination ImFont)
+struct ImFontBuildDstDataFT
+{
+    int                 SrcCount;           // Number of source fonts targeting this destination font.
+    int                 GlyphsHighest;
+    int                 GlyphsCount;
+    ImBoolVector        GlyphsSet;          // This is used to resolve collision when multiple sources are merged into a same destination font.
+};
+
+bool ImFontAtlasBuildWithFreeType(FT_Library ft_library, ImFontAtlas* atlas, unsigned int extra_flags)
 {
    IM_ASSERT(atlas->ConfigData.Size > 0);
-    IM_ASSERT(atlas->TexGlyphPadding == 1); // Not supported

    ImFontAtlasBuildRegisterDefaultCustomRects(atlas);

-    atlas->TexID = NULL;
+    // Clear atlas
+    atlas->TexID = (ImTextureID)NULL;
    atlas->TexWidth = atlas->TexHeight = 0;
    atlas->TexUvScale = ImVec2(0.0f, 0.0f);
    atlas->TexUvWhitePixel = ImVec2(0.0f, 0.0f);
    atlas->ClearTexData();

-    ImVector<FreeTypeFont> fonts;
-    fonts.resize(atlas->ConfigData.Size);
+    // Temporary storage for building
+    ImVector<ImFontBuildSrcDataFT> src_tmp_array;
+    ImVector<ImFontBuildDstDataFT> dst_tmp_array;
+    src_tmp_array.resize(atlas->ConfigData.Size);
+    dst_tmp_array.resize(atlas->Fonts.Size);
+    memset(src_tmp_array.Data, 0, (size_t)src_tmp_array.size_in_bytes());
+    memset(dst_tmp_array.Data, 0, (size_t)dst_tmp_array.size_in_bytes());

-    ImVec2 max_glyph_size(1.0f, 1.0f);
-
-    // Count glyphs/ranges, initialize font
-    int total_glyphs_count = 0;
-    int total_ranges_count = 0;
-    for (int input_i = 0; input_i < atlas->ConfigData.Size; input_i++) 
+    // 1. Initialize font loading structure, check font data validity
+    for (int src_i = 0; src_i < atlas->ConfigData.Size; src_i++)
    {
-        ImFontConfig& cfg = atlas->ConfigData[input_i];
-        FreeTypeFont& font_face = fonts[input_i];
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        ImFontConfig& cfg = atlas->ConfigData[src_i];
+        FreeTypeFont& font_face = src_tmp.Font;
        IM_ASSERT(cfg.DstFont && (!cfg.DstFont->IsLoaded() || cfg.DstFont->ContainerAtlas == atlas));

-        if (!font_face.Init(cfg, extra_flags))
+        // Find index from cfg.DstFont (we allow the user to set cfg.DstFont. Also it makes casual debugging nicer than when storing indices)
+        src_tmp.DstIndex = -1;
+        for (int output_i = 0; output_i < atlas->Fonts.Size && src_tmp.DstIndex == -1; output_i++)
+            if (cfg.DstFont == atlas->Fonts[output_i])
+                src_tmp.DstIndex = output_i;
+        IM_ASSERT(src_tmp.DstIndex != -1); // cfg.DstFont not pointing within atlas->Fonts[] array?
+        if (src_tmp.DstIndex == -1)
            return false;

-        max_glyph_size.x = ImMax(max_glyph_size.x, font_face.Info.MaxAdvanceWidth);
-        max_glyph_size.y = ImMax(max_glyph_size.y, font_face.Info.Ascender - font_face.Info.Descender);
+        // Load font
+        if (!font_face.InitFont(ft_library, cfg, extra_flags))
+            return false;

-        if (!cfg.GlyphRanges)
-            cfg.GlyphRanges = atlas->GetGlyphRangesDefault();
-        for (const ImWchar* in_range = cfg.GlyphRanges; in_range[0] && in_range[ 1 ]; in_range += 2, total_ranges_count++) 
-            total_glyphs_count += (in_range[1] - in_range[0]) + 1;
+        // Measure highest codepoints
+        ImFontBuildDstDataFT& dst_tmp = dst_tmp_array[src_tmp.DstIndex];
+        src_tmp.SrcRanges = cfg.GlyphRanges ? cfg.GlyphRanges : atlas->GetGlyphRangesDefault();
+        for (const ImWchar* src_range = src_tmp.SrcRanges; src_range[0] && src_range[1]; src_range += 2)
+            src_tmp.GlyphsHighest = ImMax(src_tmp.GlyphsHighest, (int)src_range[1]);
+        dst_tmp.SrcCount++;
+        dst_tmp.GlyphsHighest = ImMax(dst_tmp.GlyphsHighest, src_tmp.GlyphsHighest);
    }

-    // We need a width for the skyline algorithm. Using a dumb heuristic here to decide of width. User can override TexDesiredWidth and TexGlyphPadding if they wish.
-    // Width doesn't really matter much, but some API/GPU have texture size limitations and increasing width can decrease height.
-    atlas->TexWidth = (atlas->TexDesiredWidth > 0) ? atlas->TexDesiredWidth : (total_glyphs_count > 4000) ? 4096 : (total_glyphs_count > 2000) ? 2048 : (total_glyphs_count > 1000) ? 1024 : 512;
+    // 2. For every requested codepoint, check for their presence in the font data, and handle redundancy or overlaps between source fonts to avoid unused glyphs.
+    int total_glyphs_count = 0;
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
+    {
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        ImFontBuildDstDataFT& dst_tmp = dst_tmp_array[src_tmp.DstIndex];
+        ImFontConfig& cfg = atlas->ConfigData[src_i];
+        src_tmp.GlyphsSet.Resize(src_tmp.GlyphsHighest + 1);
+        if (dst_tmp.SrcCount > 1 && dst_tmp.GlyphsSet.Storage.empty())
+            dst_tmp.GlyphsSet.Resize(dst_tmp.GlyphsHighest + 1);

-    // We don't do the original first pass to determine texture height, but just rough estimate.
-    // Looks ugly inaccurate and excessive, but AFAIK with FreeType we actually need to render glyphs to get exact sizes.
-    // Alternatively, we could just render all glyphs into a big shadow buffer, get their sizes, do the rectangle packing and just copy back from the 
-    // shadow buffer to the texture buffer. Will give us an accurate texture height, but eat a lot of temp memory. Probably no one will notice.)
-    const int total_rects = total_glyphs_count + atlas->CustomRects.size();
-    float min_rects_per_row = ceilf((atlas->TexWidth / (max_glyph_size.x + 1.0f)));
-    float min_rects_per_column = ceilf(total_rects / min_rects_per_row);
-    atlas->TexHeight = (int)(min_rects_per_column * (max_glyph_size.y + 1.0f));
+        for (const ImWchar* src_range = src_tmp.SrcRanges; src_range[0] && src_range[1]; src_range += 2)
+            for (int codepoint = src_range[0]; codepoint <= src_range[1]; codepoint++)
+            {
+                if (cfg.MergeMode && dst_tmp.GlyphsSet.GetBit(codepoint))               // Don't overwrite existing glyphs. We could make this an option (e.g. MergeOverwrite)
+                    continue;
+                uint32_t glyph_index = FT_Get_Char_Index(src_tmp.Font.Face, codepoint); // It is actually in the font? (FIXME-OPT: We are not storing the glyph_index..)
+                if (glyph_index == 0)
+                    continue;

-    // Create texture
+                // Add to avail set/counters
+                src_tmp.GlyphsCount++;
+                dst_tmp.GlyphsCount++;
+                src_tmp.GlyphsSet.SetBit(codepoint, true);
+                if (dst_tmp.SrcCount > 1)
+                    dst_tmp.GlyphsSet.SetBit(codepoint, true);
+                total_glyphs_count++;
+            }
+    }
+
+    // 3. Unpack our bit map into a flat list (we now have all the Unicode points that we know are requested _and_ available _and_ not overlapping another)
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
+    {
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        src_tmp.GlyphsList.reserve(src_tmp.GlyphsCount);
+
+        IM_ASSERT(sizeof(src_tmp.GlyphsSet.Storage.Data[0]) == sizeof(int));
+        const int* it_begin = src_tmp.GlyphsSet.Storage.begin();
+        const int* it_end = src_tmp.GlyphsSet.Storage.end();
+        for (const int* it = it_begin; it < it_end; it++)
+            if (int entries_32 = *it)
+                for (int bit_n = 0; bit_n < 32; bit_n++)
+                    if (entries_32 & (1 << bit_n))
+                    {
+                        ImFontBuildSrcGlyphFT src_glyph;
+                        memset(&src_glyph, 0, sizeof(src_glyph));
+                        src_glyph.Codepoint = (ImWchar)(((it - it_begin) << 5) + bit_n);
+                        //src_glyph.GlyphIndex = 0; // FIXME-OPT: We had this info in the previous step and lost it..
+                        src_tmp.GlyphsList.push_back(src_glyph);
+                    }
+        src_tmp.GlyphsSet.Clear();
+        IM_ASSERT(src_tmp.GlyphsList.Size == src_tmp.GlyphsCount);
+    }
+    for (int dst_i = 0; dst_i < dst_tmp_array.Size; dst_i++)
+        dst_tmp_array[dst_i].GlyphsSet.Clear();
+    dst_tmp_array.clear();
+
+    // Allocate packing character data and flag packed characters buffer as non-packed (x0=y0=x1=y1=0)
+    // (We technically don't need to zero-clear buf_rects, but let's do it for the sake of sanity)
+    ImVector<stbrp_rect> buf_rects;
+    buf_rects.resize(total_glyphs_count);
+    memset(buf_rects.Data, 0, (size_t)buf_rects.size_in_bytes());
+
+    // Allocate temporary rasterization data buffers. 
+    // We could not find a way to retrieve accurate glyph size without rendering them.
+    // (e.g. slot->metrics->width not always matching bitmap->width, especially considering the Oblique transform)
+    // We allocate in chunks of 256 KB to not waste too much extra memory ahead. Hopefully users of FreeType won't find the temporary allocations.
+    const int BITMAP_BUFFERS_CHUNK_SIZE = 256 * 1024;
+    int buf_bitmap_current_used_bytes = 0;
+    ImVector<unsigned char*> buf_bitmap_buffers;
+    buf_bitmap_buffers.push_back((unsigned char*)ImGui::MemAlloc(BITMAP_BUFFERS_CHUNK_SIZE));
+
+    // 4. Gather glyphs sizes so we can pack them in our virtual canvas.
+    // 8. Render/rasterize font characters into the texture
+    int total_surface = 0;
+    int buf_rects_out_n = 0;
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
+    {
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        ImFontConfig& cfg = atlas->ConfigData[src_i];
+        if (src_tmp.GlyphsCount == 0)
+            continue;
+
+        src_tmp.Rects = &buf_rects[buf_rects_out_n];
+        buf_rects_out_n += src_tmp.GlyphsCount;
+
+        // Compute multiply table if requested
+        const bool multiply_enabled = (cfg.RasterizerMultiply != 1.0f);
+        unsigned char multiply_table[256];
+        if (multiply_enabled)
+            ImFontAtlasBuildMultiplyCalcLookupTable(multiply_table, cfg.RasterizerMultiply);
+
+        // Gather the sizes of all rectangles we will need to pack
+        const int padding = atlas->TexGlyphPadding;
+        for (int glyph_i = 0; glyph_i < src_tmp.GlyphsList.Size; glyph_i++)
+        {
+            ImFontBuildSrcGlyphFT& src_glyph = src_tmp.GlyphsList[glyph_i];
+
+            const FT_Glyph_Metrics* metrics = src_tmp.Font.LoadGlyph(src_glyph.Codepoint);
+            IM_ASSERT(metrics != NULL);
+            if (metrics == NULL)
+                continue;
+
+            // Render glyph into a bitmap (currently held by FreeType)
+            const FT_Bitmap* ft_bitmap = src_tmp.Font.RenderGlyphAndGetInfo(&src_glyph.Info);
+            IM_ASSERT(ft_bitmap);
+
+            // Allocate new temporary chunk if needed
+            const int bitmap_size_in_bytes = src_glyph.Info.Width * src_glyph.Info.Height;
+            if (buf_bitmap_current_used_bytes + bitmap_size_in_bytes > BITMAP_BUFFERS_CHUNK_SIZE)
+            {
+                buf_bitmap_current_used_bytes = 0;
+                buf_bitmap_buffers.push_back((unsigned char*)ImGui::MemAlloc(BITMAP_BUFFERS_CHUNK_SIZE));
+            }
+
+            // Blit rasterized pixels to our temporary buffer and keep a pointer to it.
+            src_glyph.BitmapData = buf_bitmap_buffers.back() + buf_bitmap_current_used_bytes;
+            buf_bitmap_current_used_bytes += bitmap_size_in_bytes;
+            src_tmp.Font.BlitGlyph(ft_bitmap, src_glyph.BitmapData, src_glyph.Info.Width * 1, multiply_enabled ? multiply_table : NULL);
+
+            src_tmp.Rects[glyph_i].w = (stbrp_coord)(src_glyph.Info.Width + padding);
+            src_tmp.Rects[glyph_i].h = (stbrp_coord)(src_glyph.Info.Height + padding);
+            total_surface += src_tmp.Rects[glyph_i].w * src_tmp.Rects[glyph_i].h;
+        }
+    }
+
+    // We need a width for the skyline algorithm, any width!
+    // The exact width doesn't really matter much, but some API/GPU have texture size limitations and increasing width can decrease height.
+    // User can override TexDesiredWidth and TexGlyphPadding if they wish, otherwise we use a simple heuristic to select the width based on expected surface.
+    const int surface_sqrt = (int)ImSqrt((float)total_surface) + 1;
+    atlas->TexHeight = 0;
+    if (atlas->TexDesiredWidth > 0)
+        atlas->TexWidth = atlas->TexDesiredWidth;
+    else
+        atlas->TexWidth = (surface_sqrt >= 4096*0.7f) ? 4096 : (surface_sqrt >= 2048*0.7f) ? 2048 : (surface_sqrt >= 1024*0.7f) ? 1024 : 512;
+
+    // 5. Start packing
+    // Pack our extra data rectangles first, so it will be on the upper-left corner of our texture (UV will have small values).
+    const int TEX_HEIGHT_MAX = 1024 * 32;
+    const int num_nodes_for_packing_algorithm = atlas->TexWidth - atlas->TexGlyphPadding;
+    ImVector<stbrp_node> pack_nodes;
+    pack_nodes.resize(num_nodes_for_packing_algorithm);
+    stbrp_context pack_context;
+    stbrp_init_target(&pack_context, atlas->TexWidth, TEX_HEIGHT_MAX, pack_nodes.Data, pack_nodes.Size);
+    ImFontAtlasBuildPackCustomRects(atlas, &pack_context);
+
+    // 6. Pack each source font. No rendering yet, we are working with rectangles in an infinitely tall texture at this point.
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
+    {
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        if (src_tmp.GlyphsCount == 0)
+            continue;
+
+        stbrp_pack_rects(&pack_context, src_tmp.Rects, src_tmp.GlyphsCount);
+
+        // Extend texture height and mark missing glyphs as non-packed so we won't render them.
+        // FIXME: We are not handling packing failure here (would happen if we got off TEX_HEIGHT_MAX or if a single if larger than TexWidth?)
+        for (int glyph_i = 0; glyph_i < src_tmp.GlyphsCount; glyph_i++)
+            if (src_tmp.Rects[glyph_i].was_packed)
+                atlas->TexHeight = ImMax(atlas->TexHeight, src_tmp.Rects[glyph_i].y + src_tmp.Rects[glyph_i].h);
+    }
+
+    // 7. Allocate texture
    atlas->TexHeight = (atlas->Flags & ImFontAtlasFlags_NoPowerOfTwoHeight) ? (atlas->TexHeight + 1) : ImUpperPowerOfTwo(atlas->TexHeight);
    atlas->TexUvScale = ImVec2(1.0f / atlas->TexWidth, 1.0f / atlas->TexHeight);
    atlas->TexPixelsAlpha8 = (unsigned char*)ImGui::MemAlloc(atlas->TexWidth * atlas->TexHeight);
    memset(atlas->TexPixelsAlpha8, 0, atlas->TexWidth * atlas->TexHeight);

-    // Start packing
-    ImVector<stbrp_node> pack_nodes;
-    pack_nodes.resize(total_rects);
-    stbrp_context context;
-    stbrp_init_target(&context, atlas->TexWidth, atlas->TexHeight, pack_nodes.Data, total_rects);
-
-    // Pack our extra data rectangles first, so it will be on the upper-left corner of our texture (UV will have small values).
-    ImFontAtlasBuildPackCustomRects(atlas, &context);
-
-    // Render characters, setup ImFont and glyphs for runtime
-    for (int input_i = 0; input_i < atlas->ConfigData.Size; input_i++)
+    // 8. Copy rasterized font characters back into the main texture
+    // 9. Setup ImFont and glyphs for runtime
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
    {
-        ImFontConfig& cfg = atlas->ConfigData[input_i];
-        FreeTypeFont& font_face = fonts[input_i];
-        ImFont* dst_font = cfg.DstFont;
-        if (cfg.MergeMode)
-            dst_font->BuildLookupTable();
+        ImFontBuildSrcDataFT& src_tmp = src_tmp_array[src_i];
+        if (src_tmp.GlyphsCount == 0)
+            continue;

-        const float ascent = font_face.Info.Ascender;
-        const float descent = font_face.Info.Descender;
+        ImFontConfig& cfg = atlas->ConfigData[src_i];
+        ImFont* dst_font = cfg.DstFont; // We can have multiple input fonts writing into a same destination font (when using MergeMode=true)
+
+        const float ascent = src_tmp.Font.Info.Ascender;
+        const float descent = src_tmp.Font.Info.Descender;
        ImFontAtlasBuildSetupFont(atlas, dst_font, &cfg, ascent, descent);
        const float font_off_x = cfg.GlyphOffset.x;
        const float font_off_y = cfg.GlyphOffset.y + (float)(int)(dst_font->Ascent + 0.5f);

-        bool multiply_enabled = (cfg.RasterizerMultiply != 1.0f);
-        unsigned char multiply_table[256];
-        if (multiply_enabled)
-            ImFontAtlasBuildMultiplyCalcLookupTable(multiply_table, cfg.RasterizerMultiply);
-
-        for (const ImWchar* in_range = cfg.GlyphRanges; in_range[0] && in_range[1]; in_range += 2) 
+        const int padding = atlas->TexGlyphPadding;
+        for (int glyph_i = 0; glyph_i < src_tmp.GlyphsCount; glyph_i++)
        {
-            for (uint32_t codepoint = in_range[0]; codepoint <= in_range[1]; ++codepoint) 
-            {
-                if (cfg.MergeMode && dst_font->FindGlyphNoFallback((unsigned short)codepoint))
-                    continue;
+            ImFontBuildSrcGlyphFT& src_glyph = src_tmp.GlyphsList[glyph_i];
+            stbrp_rect& pack_rect = src_tmp.Rects[glyph_i];
+            IM_ASSERT(pack_rect.was_packed);

-                FT_Glyph ft_glyph = NULL;
-                FT_BitmapGlyph ft_glyph_bitmap = NULL; // NB: will point to bitmap within FT_Glyph
-                GlyphInfo glyph_info;
-                if (!font_face.CalcGlyphInfo(codepoint, glyph_info, ft_glyph, ft_glyph_bitmap))
-                    continue;
+            GlyphInfo& info = src_glyph.Info;
+            IM_ASSERT(info.Width + padding <= pack_rect.w);
+            IM_ASSERT(info.Height + padding <= pack_rect.h);
+            const int tx = pack_rect.x + padding;
+            const int ty = pack_rect.y + padding;

-                // Pack rectangle
-                stbrp_rect rect;
-                rect.w = (uint16_t)glyph_info.Width + 1; // Account for texture filtering
-                rect.h = (uint16_t)glyph_info.Height + 1;
-                stbrp_pack_rects(&context, &rect, 1);
+            // Blit from temporary buffer to final texture
+            size_t blit_src_stride = (size_t)src_glyph.Info.Width;
+            size_t blit_dst_stride = (size_t)atlas->TexWidth;
+            unsigned char* blit_src = src_glyph.BitmapData;
+            unsigned char* blit_dst = atlas->TexPixelsAlpha8 + (ty * blit_dst_stride) + tx;
+            for (int y = info.Height; y > 0; y--, blit_dst += blit_dst_stride, blit_src += blit_src_stride)
+                memcpy(blit_dst, blit_src, blit_src_stride);

-                // Copy rasterized pixels to main texture
-                uint8_t* blit_dst = atlas->TexPixelsAlpha8 + rect.y * atlas->TexWidth + rect.x;
-                font_face.BlitGlyph(ft_glyph_bitmap, blit_dst, atlas->TexWidth, multiply_enabled ? multiply_table : NULL);
-                FT_Done_Glyph(ft_glyph);
-
-                float char_advance_x_org = glyph_info.AdvanceX;
-                float char_advance_x_mod = ImClamp(char_advance_x_org, cfg.GlyphMinAdvanceX, cfg.GlyphMaxAdvanceX);
-                float char_off_x = font_off_x;
-                if (char_advance_x_org != char_advance_x_mod)
-                    char_off_x += cfg.PixelSnapH ? (float)(int)((char_advance_x_mod - char_advance_x_org) * 0.5f) : (char_advance_x_mod - char_advance_x_org) * 0.5f;
-
-                // Register glyph
-                dst_font->AddGlyph((ImWchar)codepoint, 
-                    glyph_info.OffsetX + char_off_x, 
-                    glyph_info.OffsetY + font_off_y, 
-                    glyph_info.OffsetX + char_off_x + glyph_info.Width, 
-                    glyph_info.OffsetY + font_off_y + glyph_info.Height,
-                    rect.x / (float)atlas->TexWidth, 
-                    rect.y / (float)atlas->TexHeight, 
-                    (rect.x + glyph_info.Width) / (float)atlas->TexWidth, 
-                    (rect.y + glyph_info.Height) / (float)atlas->TexHeight,
-                    char_advance_x_mod);
-            }
+            float char_advance_x_org = info.AdvanceX;
+            float char_advance_x_mod = ImClamp(char_advance_x_org, cfg.GlyphMinAdvanceX, cfg.GlyphMaxAdvanceX);
+            float char_off_x = font_off_x;
+            if (char_advance_x_org != char_advance_x_mod)
+                char_off_x += cfg.PixelSnapH ? (float)(int)((char_advance_x_mod - char_advance_x_org) * 0.5f) : (char_advance_x_mod - char_advance_x_org) * 0.5f;
+            
+            // Register glyph
+            float x0 = info.OffsetX + char_off_x;
+            float y0 = info.OffsetY + font_off_y;
+            float x1 = x0 + info.Width;
+            float y1 = y0 + info.Height;
+            float u0 = (tx) / (float)atlas->TexWidth;
+            float v0 = (ty) / (float)atlas->TexHeight;
+            float u1 = (tx + info.Width) / (float)atlas->TexWidth;
+            float v1 = (ty + info.Height) / (float)atlas->TexHeight;
+            dst_font->AddGlyph((ImWchar)src_glyph.Codepoint, x0, y0, x1, y1, u0, v0, u1, v1, char_advance_x_mod);
        }
+
+        src_tmp.Rects = NULL;
    }

    // Cleanup
-    for (int n = 0; n < fonts.Size; n++)
-        fonts[n].Shutdown();
+    for (int buf_i = 0; buf_i < buf_bitmap_buffers.Size; buf_i++)
+        ImGui::MemFree(buf_bitmap_buffers[buf_i]);
+    for (int src_i = 0; src_i < src_tmp_array.Size; src_i++)
+        src_tmp_array[src_i].~ImFontBuildSrcDataFT();

    ImFontAtlasBuildFinish(atlas);

    return true;
 }
+
+bool ImGuiFreeType::BuildFontAtlas(ImFontAtlas* atlas, unsigned int extra_flags)
+{
+    FT_Library ft_library;
+    FT_Error error = FT_Init_FreeType(&ft_library);
+    if (error != 0)
+        return false;
+
+    bool ret = ImFontAtlasBuildWithFreeType(ft_library, atlas, extra_flags);
+    FT_Done_FreeType(ft_library);
+
+    return ret;
+}
@@ -1,4 +1,4 @@
-// Wrapper to use Freetype (instead of stb_truetype) for Dear ImGui
+// Wrapper to use FreeType (instead of stb_truetype) for Dear ImGui
 // Get latest version at https://github.com/ocornut/imgui/tree/master/misc/freetype
 // Original code by @Vuhdo (Aleksei Skriabin), maintained by @ocornut

@@ -1,10 +1,11 @@
-// ImGui Platform Binding for: GLFW
+// dear imgui: Platform Binding for GLFW
 // This needs to be used along with a Renderer (e.g. OpenGL3, Vulkan..)
 // (Info: GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
+// (Requires: GLFW 3.1+)

 // Implemented features:
 //  [X] Platform: Clipboard support.
-//  [X] Platform: Gamepad navigation mapping. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
+//  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [x] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: 3 cursors types are missing from GLFW.
 //  [X] Platform: Keyboard arrays indexed using GLFW_KEY_* codes, e.g. ImGui::IsKeyPressed(GLFW_KEY_SPACE).

@@ -14,6 +15,8 @@

 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2018-11-30: Misc: Setting up io.BackendPlatformName so it can be displayed in the About Window.
+//  2018-11-07: Inputs: When installing our GLFW callbacks, we save user's previously installed ones - if any - and chain call them.
 //  2018-08-01: Inputs: Workaround for Emscripten which doesn't seem to handle focus related calls.
 //  2018-06-29: Inputs: Added support for the ImGuiMouseCursor_Hand cursor.
 //  2018-06-08: Misc: Extracted imgui_impl_glfw.cpp/.h away from the old combined GLFW+OpenGL/Vulkan examples.
@@ -51,11 +54,17 @@ enum GlfwClientApi
    GlfwClientApi_OpenGL,
    GlfwClientApi_Vulkan
 };
-static GLFWwindow*      g_Window = NULL;
-static GlfwClientApi    g_ClientApi = GlfwClientApi_Unknown;
-static double           g_Time = 0.0;
-static bool             g_MouseJustPressed[5] = { false, false, false, false, false };
-static GLFWcursor*      g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };
+static GLFWwindow*          g_Window = NULL;
+static GlfwClientApi        g_ClientApi = GlfwClientApi_Unknown;
+static double               g_Time = 0.0;
+static bool                 g_MouseJustPressed[5] = { false, false, false, false, false };
+static GLFWcursor*          g_MouseCursors[ImGuiMouseCursor_COUNT] = { 0 };
+
+// Chain GLFW callbacks: our callbacks will call the user's previously installed callbacks, if any.
+static GLFWmousebuttonfun   g_PrevUserCallbackMousebutton = NULL;
+static GLFWscrollfun        g_PrevUserCallbackScroll = NULL;
+static GLFWkeyfun           g_PrevUserCallbackKey = NULL;
+static GLFWcharfun          g_PrevUserCallbackChar = NULL;

 static const char* ImGui_ImplGlfw_GetClipboardText(void* user_data)
 {
@@ -67,49 +76,53 @@ static void ImGui_ImplGlfw_SetClipboardText(void* user_data, const char* text)
    glfwSetClipboardString((GLFWwindow*)user_data, text);
 }

-void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow*, int button, int action, int /*mods*/)
+void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, int button, int action, int mods)
 {
+    if (g_PrevUserCallbackMousebutton != NULL)
+        g_PrevUserCallbackMousebutton(window, button, action, mods);
+
    if (action == GLFW_PRESS && button >= 0 && button < IM_ARRAYSIZE(g_MouseJustPressed))
        g_MouseJustPressed[button] = true;
 }

-void ImGui_ImplGlfw_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
+void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset)
 {
+    if (g_PrevUserCallbackScroll != NULL)
+        g_PrevUserCallbackScroll(window, xoffset, yoffset);
+
    ImGuiIO& io = ImGui::GetIO();
    io.MouseWheelH += (float)xoffset;
    io.MouseWheel += (float)yoffset;
 }

-void ImGui_ImplGlfw_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
+void ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
 {
+    if (g_PrevUserCallbackKey != NULL) 
+        g_PrevUserCallbackKey(window, key, scancode, action, mods);
+
    ImGuiIO& io = ImGui::GetIO();
    if (action == GLFW_PRESS)
        io.KeysDown[key] = true;
    if (action == GLFW_RELEASE)
        io.KeysDown[key] = false;

-    (void)mods; // Modifiers are not reliable across systems
+    // Modifiers are not reliable across systems
    io.KeyCtrl = io.KeysDown[GLFW_KEY_LEFT_CONTROL] || io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
    io.KeyShift = io.KeysDown[GLFW_KEY_LEFT_SHIFT] || io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
    io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] || io.KeysDown[GLFW_KEY_RIGHT_ALT];
    io.KeySuper = io.KeysDown[GLFW_KEY_LEFT_SUPER] || io.KeysDown[GLFW_KEY_RIGHT_SUPER];
 }

-void ImGui_ImplGlfw_CharCallback(GLFWwindow*, unsigned int c)
+void ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c)
 {
+    if (g_PrevUserCallbackChar != NULL)
+        g_PrevUserCallbackChar(window, c);
+
    ImGuiIO& io = ImGui::GetIO();
    if (c > 0 && c < 0x10000)
        io.AddInputCharacter((unsigned short)c);
 }

-void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
-{
-    glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
-    glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
-    glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
-    glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
-}
-
 static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, GlfwClientApi client_api)
 {
    g_Window = window;
@@ -119,6 +132,7 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
    ImGuiIO& io = ImGui::GetIO();
    io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
    io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
+    io.BackendPlatformName = "imgui_impl_glfw";

    // Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array.
    io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
@@ -159,8 +173,18 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
    g_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);  // FIXME: GLFW doesn't have this.
    g_MouseCursors[ImGuiMouseCursor_Hand] = glfwCreateStandardCursor(GLFW_HAND_CURSOR);
    
+    // Chain GLFW callbacks: our callbacks will call the user's previously installed callbacks, if any.
+    g_PrevUserCallbackMousebutton = NULL;
+    g_PrevUserCallbackScroll = NULL;
+    g_PrevUserCallbackKey = NULL;
+    g_PrevUserCallbackChar = NULL;
    if (install_callbacks)
-        ImGui_ImplGlfw_InstallCallbacks(window);
+    {
+        g_PrevUserCallbackMousebutton = glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
+        g_PrevUserCallbackScroll = glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
+        g_PrevUserCallbackKey = glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
+        g_PrevUserCallbackChar = glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
+    }

    g_ClientApi = client_api;
    return true;
@@ -244,9 +268,9 @@ static void ImGui_ImplGlfw_UpdateMouseCursor()
 void ImGui_ImplGlfw_NewFrame()
 {
    ImGuiIO& io = ImGui::GetIO();
-    IM_ASSERT(io.Fonts->IsBuilt());     // Font atlas needs to be built, call renderer _NewFrame() function e.g. ImGui_ImplOpenGL3_NewFrame() 
+    IM_ASSERT(io.Fonts->IsBuilt() && "Font atlas not built! It is generally built by the renderer back-end. Missing call to renderer _NewFrame() function? e.g. ImGui_ImplOpenGL3_NewFrame().");

-    // Setup display size
+    // Setup display size (every frame to accommodate for window resizing)
    int w, h;
    int display_w, display_h;
    glfwGetWindowSize(g_Window, &w, &h);
@@ -1,10 +1,10 @@
-// ImGui Platform Binding for: GLFW
+// dear imgui: Platform Binding for GLFW
 // This needs to be used along with a Renderer (e.g. OpenGL3, Vulkan..)
 // (Info: GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)

 // Implemented features:
 //  [X] Platform: Clipboard support.
-//  [X] Platform: Gamepad navigation mapping. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
+//  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 //  [x] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'. FIXME: 3 cursors types are missing from GLFW.
 //  [X] Platform: Keyboard arrays indexed using GLFW_KEY_* codes, e.g. ImGui::IsKeyPressed(GLFW_KEY_SPACE).

@@ -16,6 +16,8 @@
 // The 'glsl_version' initialization parameter defaults to "#version 150" if NULL.
 // Only override if your GL version doesn't handle this GLSL version. Keep NULL if unsure!

+#pragma once
+
 struct GLFWwindow;

 IMGUI_IMPL_API bool     ImGui_ImplGlfw_InitForOpenGL(GLFWwindow* window, bool install_callbacks);
@@ -23,9 +25,8 @@ IMGUI_IMPL_API bool     ImGui_ImplGlfw_InitForVulkan(GLFWwindow* window, bool in
 IMGUI_IMPL_API void     ImGui_ImplGlfw_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplGlfw_NewFrame();

-// GLFW callbacks (installed by default if you enable 'install_callbacks' during initialization)
-// Provided here if you want to chain callbacks.
-// You can also handle inputs yourself and use those as a reference.
+// InitXXX function with 'install_callbacks=true': install GLFW callbacks. They will call user's previously installed callbacks, if any.
+// InitXXX function with 'install_callbacks=false': do not install GLFW callbacks. You will need to call them yourself from your own GLFW callbacks.
 IMGUI_IMPL_API void     ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, int button, int action, int mods);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset);
 IMGUI_IMPL_API void     ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods);
@@ -1,4 +1,4 @@
-// ImGui Renderer for: OpenGL3 / OpenGL ES2 / OpenGL ES3 (modern OpenGL with shaders / programmatic pipeline)
+// dear imgui: Renderer for OpenGL3 / OpenGL ES2 / OpenGL ES3 (modern OpenGL with shaders / programmatic pipeline)
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 // (Note: We are using GL3W as a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc..)

@@ -11,6 +11,8 @@

 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
+//  2018-11-13: OpenGL: Support for GL 4.5's glClipControl(GL_UPPER_LEFT).
 //  2018-08-29: OpenGL: Added support for more OpenGL loaders: glew and glad, with comments indicative that any loader can be used.
 //  2018-08-09: OpenGL: Default to OpenGL ES 3 on iOS and Android. GLSL version default to "#version 300 ES".
 //  2018-07-30: OpenGL: Support for GLSL 300 ES and 410 core. Fixes for Emscripten compilation.
@@ -99,6 +101,9 @@ static unsigned int g_VboHandle = 0, g_ElementsHandle = 0;
 // Functions
 bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
 {
+    ImGuiIO& io = ImGui::GetIO();
+    io.BackendRendererName = "imgui_impl_opengl3";
+
    // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
 #ifdef USE_GL_ES3
    if (glsl_version == NULL)
@@ -110,6 +115,7 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
    IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersionString));
    strcpy(g_GlslVersionString, glsl_version);
    strcat(g_GlslVersionString, "\n");
+
    return true;
 }

@@ -162,6 +168,12 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
    GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
    GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
    GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);
+    bool clip_origin_lower_left = true;
+#ifdef GL_CLIP_ORIGIN
+    GLenum last_clip_origin = 0; glGetIntegerv(GL_CLIP_ORIGIN, (GLint*)&last_clip_origin); // Support for GL 4.5's glClipControl(GL_UPPER_LEFT)
+    if (last_clip_origin == GL_UPPER_LEFT)
+        clip_origin_lower_left = false;
+#endif

    // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
    glEnable(GL_BLEND);
@@ -175,7 +187,7 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
 #endif

    // Setup viewport, orthographic projection matrix
-    // Our visible imgui space lies from draw_data->DisplayPps (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
+    // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
    float L = draw_data->DisplayPos.x;
    float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
@@ -234,7 +246,10 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
                if (clip_rect.x < fb_width && clip_rect.y < fb_height && clip_rect.z >= 0.0f && clip_rect.w >= 0.0f)
                {
                    // Apply scissor/clipping rectangle
-                    glScissor((int)clip_rect.x, (int)(fb_height - clip_rect.w), (int)(clip_rect.z - clip_rect.x), (int)(clip_rect.w - clip_rect.y));
+                    if (clip_origin_lower_left)
+                        glScissor((int)clip_rect.x, (int)(fb_height - clip_rect.w), (int)(clip_rect.z - clip_rect.x), (int)(clip_rect.w - clip_rect.y));
+                    else
+                        glScissor((int)clip_rect.x, (int)clip_rect.y, (int)clip_rect.z, (int)clip_rect.w); // Support for GL 4.5's glClipControl(GL_UPPER_LEFT)

                    // Bind texture, Draw
                    glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
@@ -306,13 +321,13 @@ void ImGui_ImplOpenGL3_DestroyFontsTexture()
    }
 }

-// If you get an error please report on github. You may try different GL context version or GLSL version.
+// If you get an error please report on github. You may try different GL context version or GLSL version. See GL<>GLSL version table at the top of this file.
 static bool CheckShader(GLuint handle, const char* desc)
 {
    GLint status = 0, log_length = 0;
    glGetShaderiv(handle, GL_COMPILE_STATUS, &status);
    glGetShaderiv(handle, GL_INFO_LOG_LENGTH, &log_length);
-    if (status == GL_FALSE)
+    if ((GLboolean)status == GL_FALSE)
        fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to compile %s!\n", desc);
    if (log_length > 0)
    {
@@ -321,17 +336,17 @@ static bool CheckShader(GLuint handle, const char* desc)
        glGetShaderInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
        fprintf(stderr, "%s\n", buf.begin());
    }
-    return status == GL_TRUE;
+    return (GLboolean)status == GL_TRUE;
 }

-// If you get an error please report on github. You may try different GL context version or GLSL version.
+// If you get an error please report on GitHub. You may try different GL context version or GLSL version.
 static bool CheckProgram(GLuint handle, const char* desc)
 {
    GLint status = 0, log_length = 0;
    glGetProgramiv(handle, GL_LINK_STATUS, &status);
    glGetProgramiv(handle, GL_INFO_LOG_LENGTH, &log_length);
-    if (status == GL_FALSE)
-        fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to link %s!\n", desc);
+    if ((GLboolean)status == GL_FALSE)
+        fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to link %s! (with GLSL '%s')\n", desc, g_GlslVersionString);
    if (log_length > 0)
    {
        ImVector<char> buf;
@@ -339,7 +354,7 @@ static bool CheckProgram(GLuint handle, const char* desc)
        glGetProgramInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
        fprintf(stderr, "%s\n", buf.begin());
    }
-    return status == GL_TRUE;
+    return (GLboolean)status == GL_TRUE;
 }

 bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
@@ -1,4 +1,4 @@
-// ImGui Renderer for: OpenGL3 / OpenGL ES2 / OpenGL ES3 (modern OpenGL with shaders / programmatic pipeline)
+// dear imgui: Renderer for OpenGL3 / OpenGL ES2 / OpenGL ES3 (modern OpenGL with shaders / programmatic pipeline)
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 // (Note: We are using GL3W as a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc..)

@@ -19,6 +19,8 @@
 // On computer platform the GLSL version default to "#version 130". On OpenGL ES 3 platform it defaults to "#version 300 es"
 // Only override if your GL version doesn't handle this GLSL version. See GLSL version table at the top of imgui_impl_opengl3.cpp.

+#pragma once
+
 // Set default OpenGL loader to be gl3w
 #if !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)     \
 && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)     \