ImFontAtlas: Added support for CustomRect API to submit custom rectangles to be packed into the atlas / and map them as font glyphs

imgui.h

@@ -1413,19 +1413,29 @@ struct ImFontAtlas
     };
 
     //-------------------------------------------
-    // Custom Rectangles
+    // Custom Rectangles/Glyphs API
     //-------------------------------------------
 
-    // [Private] User rectangle for packing custom texture data into the atlas.
+    // You can request arbitrary rectangles to be packed into the atlas, for your own purposes. After calling Build(), you can query the rectangle position and render your pixels.
+    // You can also request your rectangles to be mapped as font glyph (given a font + Unicode point), so you can render e.g. custom colorful icons and use them as regular glyphs.
     struct CustomRect
     {
-        unsigned int    ID;             // Input    // User ID. <0x10000 for font mapped data (WIP/UNSUPPORTED), >=0x10000 for other texture data
+        unsigned int    ID;             // Input    // User ID. Use <0x10000 to map into a font glyph, >=0x10000 for other/internal/custom texture data.
         unsigned short  Width, Height;  // Input    // Desired rectangle dimension
         unsigned short  X, Y;           // Output   // Packed position in Atlas
-        CustomRect()            { ID = 0xFFFFFFFF; Width = Height = 0; X = Y = 0xFFFF; }
+        float           GlyphAdvanceX;  // Input    // For custom font glyphs only (ID<0x10000): glyph xadvance
+        ImVec2          GlyphOffset;    // Input    // For custom font glyphs only (ID<0x10000): glyph display offset
+        ImFont*         Font;           // Input    // For custom font glyphs only (ID<0x10000): target font
+        CustomRect()            { ID = 0xFFFFFFFF; Width = Height = 0; X = Y = 0xFFFF; GlyphAdvanceX = 0.0f; GlyphOffset = ImVec2(0,0); Font = NULL; }
         bool IsPacked() const   { return X != 0xFFFF; }
     };
 
+    IMGUI_API int       AddCustomRectRegular(unsigned int id, int width, int height);                                                                   // Id needs to be >= 0x10000. Id >= 0x80000000 are reserved for ImGui and ImDrawList
+    IMGUI_API int       AddCustomRectFontGlyph(ImFont* font, ImWchar id, int width, int height, float advance_x, const ImVec2& offset = ImVec2(0,0));   // Id needs to be < 0x10000 to register a rectangle to map into a specific font.
+    IMGUI_API void      ClearCustomRects();
+    IMGUI_API void      CalcCustomRectUV(const CustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max);
+    const CustomRect*   GetCustomRectByIndex(int index) const { if (index < 0) return NULL; return &CustomRects[index]; }
+
     //-------------------------------------------
     // Members
     //-------------------------------------------
@@ -1444,8 +1454,7 @@ struct ImFontAtlas
     ImVector<ImFont*>           Fonts;              // Hold all the fonts returned by AddFont*. Fonts[0] is the default font upon calling ImGui::NewFrame(), use ImGui::PushFont()/PopFont() to change the current font.
     ImVector<CustomRect>        CustomRects;        // Rectangles for packing custom texture data into the atlas.
     ImVector<ImFontConfig>      ConfigData;         // Internal data
-    IMGUI_API int               CustomRectRegister(unsigned int id, int width, int height);
-    IMGUI_API void              CustomRectCalcUV(const CustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max);
+    int                         CustomRectIds[1];   // Identifiers of custom texture rectangle used by ImFontAtlas/ImDrawList
 };
 
 // Font runtime data and rendering

imgui_draw.cpp

@@ -1066,7 +1066,7 @@ ImFontConfig::ImFontConfig()
 // The white texels on the top left are the ones we'll use everywhere in ImGui to render filled shapes.
 const int FONT_ATLAS_DEFAULT_TEX_DATA_W_HALF = 90;
 const int FONT_ATLAS_DEFAULT_TEX_DATA_H      = 27;
-const int FONT_ATLAS_DEFAULT_TEX_DATA_ID     = 0xF0000;
+const unsigned int FONT_ATLAS_DEFAULT_TEX_DATA_ID = 0x80000000;
 const char FONT_ATLAS_DEFAULT_TEX_DATA_PIXELS[FONT_ATLAS_DEFAULT_TEX_DATA_W_HALF * FONT_ATLAS_DEFAULT_TEX_DATA_H + 1] =
 {
     "..-         -XXXXXXX-    X    -           X           -XXXXXXX          -          XXXXXXX"
@@ -1107,6 +1107,8 @@ ImFontAtlas::ImFontAtlas()
     TexPixelsRGBA32 = NULL;
     TexWidth = TexHeight = 0;
     TexUvWhitePixel = ImVec2(0, 0);
+    for (int n = 0; n < IM_ARRAYSIZE(CustomRectIds); n++)
+        CustomRectIds[n] = -1;
 }
 
 ImFontAtlas::~ImFontAtlas()
@@ -1123,7 +1125,7 @@ void    ImFontAtlas::ClearInputData()
             ConfigData[i].FontData = NULL;
         }
 
-    // When clearing this we lose access to the font name and other information used to build the font.
+    // When clearing this we lose access to  the font name and other information used to build the font.
     for (int i = 0; i < Fonts.Size; i++)
         if (Fonts[i]->ConfigData >= ConfigData.Data && Fonts[i]->ConfigData < ConfigData.Data + ConfigData.Size)
         {
@@ -1319,8 +1321,9 @@ ImFont* ImFontAtlas::AddFontFromMemoryCompressedBase85TTF(const char* compressed
     return font;
 }
 
-int ImFontAtlas::CustomRectRegister(unsigned int id, int width, int height)
+int ImFontAtlas::AddCustomRectRegular(unsigned int id, int width, int height)
 {
+    IM_ASSERT(id >= 0x10000);
     IM_ASSERT(width > 0 && width <= 0xFFFF);
     IM_ASSERT(height > 0 && height <= 0xFFFF);
     CustomRect r;
@@ -1331,7 +1334,23 @@ int ImFontAtlas::CustomRectRegister(unsigned int id, int width, int height)
     return CustomRects.Size - 1; // Return index
 }
 
-void ImFontAtlas::CustomRectCalcUV(const CustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max)
+int ImFontAtlas::AddCustomRectFontGlyph(ImFont* font, ImWchar id, int width, int height, float advance_x, const ImVec2& offset)
+{
+    IM_ASSERT(font != NULL);
+    IM_ASSERT(width > 0 && width <= 0xFFFF);
+    IM_ASSERT(height > 0 && height <= 0xFFFF);
+    CustomRect r;
+    r.ID = id;
+    r.Width = (unsigned short)width;
+    r.Height = (unsigned short)height;
+    r.GlyphAdvanceX = advance_x;
+    r.GlyphOffset = offset;
+    r.Font = font;
+    CustomRects.push_back(r);
+    return CustomRects.Size - 1; // Return index
+}
+
+void ImFontAtlas::CalcCustomRectUV(const CustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max)
 {
     IM_ASSERT(TexWidth > 0 && TexHeight > 0);   // Font atlas needs to be built before we can calculate UV coordinates
     IM_ASSERT(rect->IsPacked());                // Make sure the rectangle has been packed
@@ -1553,9 +1572,8 @@ bool    ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
 
 void ImFontAtlasBuildRegisterDefaultCustomRects(ImFontAtlas* atlas)
 {
-    // FIXME-WIP: We should register in the constructor (but cannot because our static instances may not have allocator ready by the time they initialize). This needs to be fixed because we can expose CustomRects.
-    if (atlas->CustomRects.empty())
-        atlas->CustomRectRegister(FONT_ATLAS_DEFAULT_TEX_DATA_ID, FONT_ATLAS_DEFAULT_TEX_DATA_W_HALF*2+1, FONT_ATLAS_DEFAULT_TEX_DATA_H);
+    if (atlas->CustomRectIds[0] < 0)
+        atlas->CustomRectIds[0] = atlas->AddCustomRectRegular(FONT_ATLAS_DEFAULT_TEX_DATA_ID, FONT_ATLAS_DEFAULT_TEX_DATA_W_HALF*2+1, FONT_ATLAS_DEFAULT_TEX_DATA_H);
 }
 
 void ImFontAtlasBuildSetupFont(ImFontAtlas* atlas, ImFont* font, ImFontConfig* font_config, float ascent, float descent)
@@ -1600,7 +1618,8 @@ void ImFontAtlasBuildPackCustomRects(ImFontAtlas* atlas, void* pack_context_opaq
 
 static void ImFontAtlasBuildRenderDefaultTexData(ImFontAtlas* atlas)
 {
-    ImFontAtlas::CustomRect& r = atlas->CustomRects[0];
+    IM_ASSERT(atlas->CustomRectIds[0] >= 0);
+    ImFontAtlas::CustomRect& r = atlas->CustomRects[atlas->CustomRectIds[0]];
     IM_ASSERT(r.ID == FONT_ATLAS_DEFAULT_TEX_DATA_ID);
     IM_ASSERT(r.Width == FONT_ATLAS_DEFAULT_TEX_DATA_W_HALF*2+1);
     IM_ASSERT(r.Height == FONT_ATLAS_DEFAULT_TEX_DATA_H);
@@ -1653,6 +1672,19 @@ void ImFontAtlasBuildFinish(ImFontAtlas* atlas)
     // Render into our custom data block
     ImFontAtlasBuildRenderDefaultTexData(atlas);
 
+    // Register custom rectangle glyphs
+    for (int i = 0; i < atlas->CustomRects.Size; i++)
+    {
+        const ImFontAtlas::CustomRect& r = atlas->CustomRects[i];
+        if (r.Font == NULL || r.ID > 0x10000)
+            continue;
+
+        IM_ASSERT(r.Font->ContainerAtlas == atlas);
+        ImVec2 uv0, uv1;
+        atlas->CalcCustomRectUV(&r, &uv0, &uv1);
+        r.Font->AddGlyph((ImWchar)r.ID, r.GlyphOffset.x, r.GlyphOffset.y, r.GlyphOffset.x + r.Width, r.GlyphOffset.y + r.Height, uv0.x, uv0.y, uv1.x, uv1.y, r.GlyphAdvanceX);
+    }
+
     // Build all fonts lookup tables
     for (int i = 0; i < atlas->Fonts.Size; i++)
         atlas->Fonts[i]->BuildLookupTable();
@@ -1929,7 +1961,7 @@ void ImFont::AddGlyph(ImWchar codepoint, float x0, float y0, float x1, float y1,
     glyph.V0 = v0; 
     glyph.U1 = u1; 
     glyph.V1 = v1;
-    glyph.AdvanceX = (advance_x + ConfigData->GlyphExtraSpacing.x);  // Bake spacing into AdvanceX
+    glyph.AdvanceX = advance_x + ConfigData->GlyphExtraSpacing.x;  // Bake spacing into AdvanceX
 
     if (ConfigData->PixelSnapH)
         glyph.AdvanceX = (float)(int)(glyph.AdvanceX + 0.5f);