Document/workaround an issue using IMGUI_DISABLE_STB_TRUETYPE_IMPLEMENTATION since 1.92.0. (#8794)

docs/CHANGELOG.txt

@@ -49,6 +49,8 @@ Other Changes:
 - Error Handling: minor improvements to error handling for TableGetSortSpecs()
   and TableSetBgColor() calls. (#1651, #8499)
 - Misc: fixed building with IMGUI_DISABLE_DEBUG_TOOLS only. (#8796)
+- Misc: document/workaround an issue using IMGUI_DISABLE_STB_TRUETYPE_IMPLEMENTATION
+  since 1.92.0. (#8794) [@tim-rex]
 - Misc: removed more redundant inline static linkage from imgui_internal.h to 
   facilitate using in C++ modules. (#8813, #8682, #8358) [@stripe2933]
 - CI: Added SDL3 builds to MacOS and Windows. (#8819, #8778) [@scribam]

imgui_draw.cpp

@@ -4622,6 +4622,15 @@ static bool ImGui_ImplStbTrueType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig
     return true;
 }
 
+// Since 1.92.0 (June 2025) we rely on those 3 functions which are implemented inside stb_truetype.h and require STB_TRUETYPE_IMPLEMENTATION.
+// Using IMGUI_DISABLE_STB_TRUETYPE_IMPLEMENTATION became broken, see https://github.com/ocornut/imgui/issues/8794
+// One way to fix is to remove the 'static' keywords for those 3 functions in your copy of stb_truetype.h
+#ifdef IMGUI_DISABLE_STB_TRUETYPE_IMPLEMENTATION
+extern void stbtt__h_prefilter(unsigned char* pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width);
+extern void stbtt__v_prefilter(unsigned char* pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width);
+extern float stbtt__oversample_shift(int oversample);
+#endif
+
 static bool ImGui_ImplStbTrueType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConfig* src, ImFontBaked* baked, void*, ImWchar codepoint, ImFontGlyph* out_glyph, float* out_advance_x)
 {
     // Search for first font which has the glyph

imstb_truetype.h

@@ -4017,7 +4017,8 @@ STBTT_DEF void stbtt_PackSetSkipMissingCodepoints(stbtt_pack_context *spc, int s
 
 #define STBTT__OVER_MASK  (STBTT_MAX_OVERSAMPLE-1)
 
-static void stbtt__h_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
+/*static*/
+void stbtt__h_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
 {
    unsigned char buffer[STBTT_MAX_OVERSAMPLE];
    int safe_w = w - kernel_width;
@@ -4079,7 +4080,8 @@ static void stbtt__h_prefilter(unsigned char *pixels, int w, int h, int stride_i
    }
 }
 
-static void stbtt__v_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
+/*static*/
+void stbtt__v_prefilter(unsigned char *pixels, int w, int h, int stride_in_bytes, unsigned int kernel_width)
 {
    unsigned char buffer[STBTT_MAX_OVERSAMPLE];
    int safe_h = h - kernel_width;
@@ -4141,7 +4143,8 @@ static void stbtt__v_prefilter(unsigned char *pixels, int w, int h, int stride_i
    }
 }
 
-static float stbtt__oversample_shift(int oversample)
+/*static*/
+float stbtt__oversample_shift(int oversample)
 {
    if (!oversample)
       return 0.0f;