Add ImFontConfig::GlyphExtraAdvanceX as a replacement for GlyphExtraSpacing.x (ocornut#242)

Partly restore 1a31e31.

Author: ocornut

docs/CHANGELOG.txt

@@ -41,8 +41,7 @@ HOW TO UPDATE?
 
 Breaking changes:
 
-- Removed ImFontConfig::GlyphExtraSpacing option which seems largely obsolete and
-  unused. If you were using this please report it! (#242).
+- Renamed ImFontConfig::GlyphExtraSpacing.x option to GlyphExtraAdvanceX. (#242)
 
 Other changes:
 

imgui.cpp

@@ -430,7 +430,7 @@ CODE
  When you are not sure about an old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
- - 2025/02/03 (1.91.9) - removed ImFontConfig::GlyphExtraSpacing option which seems largely obsolete and unused. If you were using this please report it!
+ - 2025/02/06 (1.91.9) - renamed ImFontConfig::GlyphExtraSpacing.x to ImFontConfig::GlyphExtraAdvanceX.
  - 2025/01/22 (1.91.8) - removed ImGuiColorEditFlags_AlphaPreview (made value 0): it is now the default behavior.
                          prior to 1.91.8: alpha was made opaque in the preview by default _unless_ using ImGuiColorEditFlags_AlphaPreview. We now display the preview as transparent by default. You can use ImGuiColorEditFlags_AlphaOpaque to use old behavior.
                          the new flags (ImGuiColorEditFlags_AlphaOpaque, ImGuiColorEditFlags_AlphaNoBg + existing ImGuiColorEditFlags_AlphaPreviewHalf) may be combined better and allow finer controls:

imgui.h

@@ -29,7 +29,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.91.9 WIP"
-#define IMGUI_VERSION_NUM   19182
+#define IMGUI_VERSION_NUM   19183
 #define IMGUI_HAS_TABLE
 
 /*
@@ -3257,11 +3257,12 @@ struct ImFontConfig
     int             OversampleH;            // 0 (2)    // Rasterize at higher quality for sub-pixel positioning. 0 == auto == 1 or 2 depending on size. Note the difference between 2 and 3 is minimal. You can reduce this to 1 for large glyphs save memory. Read https://github.com/nothings/stb/blob/master/tests/oversample/README.md for details.
     int             OversampleV;            // 0 (1)    // Rasterize at higher quality for sub-pixel positioning. 0 == auto == 1. This is not really useful as we don't use sub-pixel positions on the Y axis.
     float           SizePixels;             //          // Size in pixels for rasterizer (more or less maps to the resulting font height).
-    //ImVec2        GlyphExtraSpacing;      // 0, 0     // (REMOVED AT IT SEEMS LARGELY OBSOLETE. PLEASE REPORT IF YOU WERE USING THIS). Extra spacing (in pixels) between glyphs when rendered: essentially add to glyph->AdvanceX. Only X axis is supported for now.
+    //ImVec2        GlyphExtraSpacing;      // 0, 0     // (REMOVED IN 1.91.9: use GlyphExtraAdvanceX)
     ImVec2          GlyphOffset;            // 0, 0     // Offset all glyphs from this font input.
     const ImWchar*  GlyphRanges;            // NULL     // THE ARRAY DATA NEEDS TO PERSIST AS LONG AS THE FONT IS ALIVE. Pointer to a user-provided list of Unicode range (2 value per range, values are inclusive, zero-terminated list).
     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
+    float           GlyphExtraAdvanceX;     // 0        // Extra spacing (in pixels) between glyphs. Please contact us if you are using this.
     unsigned int    FontBuilderFlags;       // 0        // Settings for custom font builder. THIS IS BUILDER IMPLEMENTATION DEPENDENT. Leave as zero if unsure.
     float           RasterizerMultiply;     // 1.0f     // Linearly brighten (>1.0f) or darken (<1.0f) font output. Brightening small fonts may be a good workaround to make them more readable. This is a silly thing we may remove in the future.
     float           RasterizerDensity;      // 1.0f     // DPI scale for rasterization, not altering other font metrics: make it easy to swap between e.g. a 100% and a 400% fonts for a zooming display. IMPORTANT: If you increase this it is expected that you increase font scale accordingly, otherwise quality may look lowered.

imgui_draw.cpp

@@ -3858,6 +3858,9 @@ void ImFont::AddGlyph(const ImFontConfig* cfg, ImWchar codepoint, float x0, floa
         // Snap to pixel
         if (cfg->PixelSnapH)
             advance_x = IM_ROUND(advance_x);
+
+        // Bake extra spacing
+        advance_x += cfg->GlyphExtraAdvanceX;
     }
 
     int glyph_idx = Glyphs.Size;