Fonts: (Breaking) Rename ImGuiFreeType:: flags to ImGuiFreeTypeBuilderFlags_XXX. Remove ImGuiFreeType::BuildFontAtlas() flags. Rename ImFontConfig::RasterizerFlags to FontBuilderFlags. Add ImFontBuilderIO (opaque). Amend 53d59f3 with a dozen of small fixes.

imgui.h

@@ -125,6 +125,7 @@ struct ImDrawListSplitter;          // Helper to split a draw list into differen
 struct ImDrawVert;                  // A single vertex (pos + uv + col = 20 bytes by default. Override layout with IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT)
 struct ImFont;                      // Runtime data for a single font within a parent ImFontAtlas
 struct ImFontAtlas;                 // Runtime data for multiple fonts, bake multiple fonts into a single texture, TTF/OTF font loader
+struct ImFontBuilderIO;             // Opaque interface to a font builder (stb_truetype or FreeType).
 struct ImFontConfig;                // Configuration data when adding a font or merging fonts
 struct ImFontGlyph;                 // A single font glyph (code point + coordinates within in ImFontAtlas + offset)
 struct ImFontGlyphRangesBuilder;    // Helper to build glyph ranges from text/string data
@@ -2488,7 +2489,7 @@ struct ImFontConfig
     float           GlyphMinAdvanceX;       // 0        // Minimum AdvanceX for glyphs, set Min to align font icons, set both Min/Max to enforce mono-space font
     float           GlyphMaxAdvanceX;       // FLT_MAX  // Maximum AdvanceX for glyphs
     bool            MergeMode;              // false    // Merge into previous ImFont, so you can combine multiple inputs font into one ImFont (e.g. ASCII font + icons + Japanese glyphs). You may want to use GlyphOffset.y when merge font of different heights.
-    unsigned int    RasterizerFlags;        // 0x00     // Settings for custom font rasterizer (e.g. ImGuiFreeType). Leave as zero if you aren't using one.
+    unsigned int    FontBuilderFlags;       // 0        // Settings for custom font builder. THIS IS BUILDER IMPLEMENTATION DEPENDENT. Leave as zero if unsure.
     float           RasterizerMultiply;     // 1.0f     // Brighten (>1.0f) or darken (<1.0f) font output. Brightening small fonts may be a good workaround to make them more readable.
     ImWchar         EllipsisChar;           // -1       // Explicitly specify unicode codepoint of ellipsis character. When fonts are being merged first specified ellipsis will be used.
 
@@ -2634,7 +2635,6 @@ struct ImFontAtlas
     ImTextureID                 TexID;              // User data to refer to the texture once it has been uploaded to user's graphic systems. It is passed back to you during rendering via the ImDrawCmd structure.
     int                         TexDesiredWidth;    // Texture width desired by user before Build(). Must be a power-of-two. If have many glyphs your graphics API have texture size restrictions you may want to increase texture width to decrease height.
     int                         TexGlyphPadding;    // Padding between glyphs within texture in pixels. Defaults to 1. If your rendering method doesn't rely on bilinear filtering you may set this to 0.
-    const char*                 Builder;            // Select font builder/rasterizer. Default to "stb_truetype". Set to "freetype" to enable Freetype (default if IMGUI_ENABLE_FREETYPE is defined).
 
     // [Internal]
     // NB: Access texture data via GetTexData*() calls! Which will setup a default font for you.
@@ -2649,6 +2649,10 @@ struct ImFontAtlas
     ImVector<ImFontConfig>      ConfigData;         // Configuration data
     ImVec4                      TexUvLines[IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1];  // UVs for baked anti-aliased lines
 
+    // [Internal] Font builder
+    const ImFontBuilderIO*      FontBuilderIO;      // Opaque interface to a font builder (default to stb_truetype, can be changed to use FreeType by defining IMGUI_ENABLE_FREETYPE).
+    unsigned int                FontBuilderFlags;   // Shared flags (for all fonts) for custom font builder. THIS IS BUILD IMPLEMENTATION DEPENDENT. Per-font override is also available in ImFontConfig.
+
     // [Internal] Packing data
     int                         PackIdMouseCursors; // Custom texture rectangle ID for white pixel and mouse cursors
     int                         PackIdLines;        // Custom texture rectangle ID for baked anti-aliased lines