imgui_freetype: fixed ExtraSizeScale (used by embedded ProggyForever) leading to non-pixel aligned vertical offset. (#9348, #9233) + Added ImRoundPositive64(), ImRoundSigned64().

docs/CHANGELOG.txt

@@ -77,6 +77,8 @@ Other Changes:
   - Reworked `AddFontDefault()` to use `io.DisplayFrameBufferScale` as part of the heuristic
     to select `AddFontDefaultVector()` by default, effectively using ProggyForever instead of
     ProggyClean on most Apple/Retina setups by default.
+  - imgui_freetype: Fixed blurryness rendering `AddFontDefaultVector()`. Caused by a
+    non-pixel aligned offset caused by `ExtraSizeScale`. (#9348, #9233) [@redpartizan, @RDMCz]
 - ColorEdit:
   - ColorButton, ColorEdit, ColorPicker: cancel-out alpha caused by BeginDisabled() so
     disabled color buttons have the same color as non-disabled oness. (#9511)

imgui.cpp

@@ -12080,7 +12080,7 @@ static ImVec2 CalcNextScrollFromScrollTargetAndClamp(ImGuiWindow* window)
             }
             scroll[axis] = scroll_target - center_ratio * (window->SizeFull[axis] - decoration_size[axis]);
         }
-        scroll[axis] = ImRound64(ImMax(scroll[axis], 0.0f));
+        scroll[axis] = ImRoundPositive64(ImMax(scroll[axis], 0.0f));
         if (!window->Collapsed && !window->SkipItems)
             scroll[axis] = ImMin(scroll[axis], window->ScrollMax[axis]);
     }

imgui_draw.cpp

@@ -4776,6 +4776,7 @@ static bool ImGui_ImplStbTrueType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig
         stbtt_GetFontVMetrics(&bd_font_data->FontInfo, &unscaled_ascent, &unscaled_descent, &unscaled_line_gap);
         baked->Ascent = ImCeil(unscaled_ascent * scale_for_layout);
         baked->Descent = ImFloor(unscaled_descent * scale_for_layout);
+        // FIXME: round to rasterizer density? (#9348)
     }
     return true;
 }

imgui_internal.h

@@ -537,7 +537,8 @@ inline ImVec2 ImTrunc(const ImVec2& v)                                  { return
 inline float  ImFloor(float f)                                          { return (float)((f >= 0 || (float)(int)f == f) ? (int)f : (int)f - 1); } // Decent replacement for floorf()
 inline ImVec2 ImFloor(const ImVec2& v)                                  { return ImVec2(ImFloor(v.x), ImFloor(v.y)); }
 inline float  ImTrunc64(float f)                                        { return (float)(ImS64)(f); }
-inline float  ImRound64(float f)                                        { return (float)(ImS64)(f + 0.5f); } // FIXME: Positive values only.
+inline float  ImRoundPositive64(float f)                                { return (float)(ImS64)(f + 0.5f); } // Positive values only.
+inline float  ImRoundSigned64(float f)                                  { return (float)(ImS64)(f >= 0.0f ? f + 0.5f : f - 0.5f); }
 inline float  ImCeilFast(float f)                                       { int i = (int)f; return (float)(i + (f > (float)i)); } // Consider using the bit-hack version (search for "0x1p120f").
 inline int    ImModPositive(int a, int b)                               { return (a + b) % b; }
 inline float  ImDot(const ImVec2& a, const ImVec2& b)                   { return a.x * b.x + a.y * b.y; }

misc/freetype/imgui_freetype.cpp

@@ -7,6 +7,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2026/09/25: fixed handling of ExtraSizeScale.
 //  2025/06/11: refactored for the new ImFontLoader architecture, and ImGuiBackendFlags_RendererHasTextures support.
 //  2024/10/17: added plutosvg support for SVG Fonts (seems faster/better than lunasvg). Enable by using '#define IMGUI_ENABLE_FREETYPE_PLUTOSVG'. (#7927)
 //  2023/11/13: added support for ImFontConfig::RasterizationDensity field for scaling render density without scaling metrics.
@@ -468,6 +469,8 @@ static bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* s
         //LineSpacing     = (float)FT_CEIL(metrics.height) * scale;         // The baseline-to-baseline distance. Note that it usually is larger than the sum of the ascender and descender taken as absolute values. There is also no guarantee that no glyphs extend above or below subsequent baselines when using this distance. Think of it as a value the designer of the font finds appropriate.
         //LineGap         = (float)FT_CEIL(metrics.height - metrics.ascender + metrics.descender) * scale; // The spacing in pixels between one row's descent and the next row's ascent.
         //MaxAdvanceWidth = (float)FT_CEIL(metrics.max_advance) * scale;    // This field gives the maximum horizontal cursor advance for all glyphs in the font.
+        baked->Ascent = ImRoundSigned64(baked->Ascent * rasterizer_density) / rasterizer_density;
+        baked->Descent = ImRoundSigned64(baked->Descent * rasterizer_density) / rasterizer_density;
     }
     return true;
 }