From 24f7328e5f7939c0fa9d9dd8c6cf9fd06c38540a Mon Sep 17 00:00:00 2001
From: ocornut <omarcornut@gmail.com>
Date: Tue, 17 Jun 2025 11:55:40 +0200
Subject: [PATCH] DrawList, Fonts: fixed ImFontAtlasTextureRepack() overwriting
 draw list shared data UV's etc. even when not bound. (#8694, #8465)

ImFontAtlasUpdateDrawListsSharedData() call from ImFontAtlasTextureRepack() would trigger this.
For simplicity we also track current atlas in ImDrawListSharedData, but we could probably use Font->ContainerAtlas.
---
 imgui.cpp        | 10 ++++++----
 imgui_draw.cpp   | 18 ++++++++++--------
 imgui_internal.h |  7 ++++---
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/imgui.cpp b/imgui.cpp
index 9ed61ba5d..4ace6433d 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -3932,7 +3932,7 @@ void ImGui::RenderMouseCursor(ImVec2 base_pos, float base_scale, ImGuiMouseCurso
     ImGuiContext& g = *GImGui;
     if (mouse_cursor <= ImGuiMouseCursor_None || mouse_cursor >= ImGuiMouseCursor_COUNT) // We intentionally accept out of bound values.
         mouse_cursor = ImGuiMouseCursor_Arrow;
-    ImFontAtlas* font_atlas = g.DrawListSharedData.Font->ContainerAtlas;
+    ImFontAtlas* font_atlas = g.DrawListSharedData.FontAtlas; 
     for (ImGuiViewportP* viewport : g.Viewports)
     {
         // We scale cursor with current viewport/monitor, however Windows 10 for its own hardware cursor seems to be using a different scale factor.
@@ -8813,10 +8813,12 @@ void ImGui::SetCurrentFont(ImFont* font, float font_size_before_scaling, float f
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
         IM_ASSERT(font->Scale > 0.0f);
 #endif
-        g.DrawListSharedData.Font = g.Font;
-        ImFontAtlasUpdateDrawListsSharedData(g.Font->ContainerAtlas);
+        ImFontAtlas* atlas = font->ContainerAtlas;
+        g.DrawListSharedData.FontAtlas = atlas;
+        g.DrawListSharedData.Font = font;
+        ImFontAtlasUpdateDrawListsSharedData(atlas);
         if (g.CurrentWindow != NULL)
-            g.CurrentWindow->DrawList->_SetTexture(font->ContainerAtlas->TexRef);
+            g.CurrentWindow->DrawList->_SetTexture(atlas->TexRef);
     }
 }
 
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index cd3d22ef9..3621deb46 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -2694,10 +2694,11 @@ void ImFontAtlas::ClearFonts()
     Fonts.clear_delete();
     TexIsBuilt = false;
     for (ImDrawListSharedData* shared_data : DrawListSharedDatas)
-    {
-        shared_data->Font = NULL;
-        shared_data->FontScale = shared_data->FontSize = 0.0f;
-    }
+        if (shared_data->FontAtlas == this)
+        {
+            shared_data->Font = NULL;
+            shared_data->FontScale = shared_data->FontSize = 0.0f;
+        }
 }
 
 static void ImFontAtlasBuildUpdateRendererHasTexturesFromContext(ImFontAtlas* atlas)
@@ -3914,10 +3915,11 @@ void ImFontAtlasUpdateDrawListsTextures(ImFontAtlas* atlas, ImTextureRef old_tex
 void ImFontAtlasUpdateDrawListsSharedData(ImFontAtlas* atlas)
 {
     for (ImDrawListSharedData* shared_data : atlas->DrawListSharedDatas)
-    {
-        shared_data->TexUvWhitePixel = atlas->TexUvWhitePixel;
-        shared_data->TexUvLines = atlas->TexUvLines;
-    }
+        if (shared_data->FontAtlas == atlas)
+        {
+            shared_data->TexUvWhitePixel = atlas->TexUvWhitePixel;
+            shared_data->TexUvLines = atlas->TexUvLines;
+        }
 }
 
 // Set current texture. This is mostly called from AddTexture() + to handle a failed resize.
diff --git a/imgui_internal.h b/imgui_internal.h
index fe71e49b0..b3a950c7a 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -838,9 +838,10 @@ struct IMGUI_API ImDrawListSharedData
 {
     ImVec2          TexUvWhitePixel;            // UV of white pixel in the atlas (== FontAtlas->TexUvWhitePixel)
     const ImVec4*   TexUvLines;                 // UV of anti-aliased lines in the atlas (== FontAtlas->TexUvLines)
-    ImFont*         Font;                       // Current/default font (optional, for simplified AddText overload)
-    float           FontSize;                   // Current/default font size (optional, for simplified AddText overload)
-    float           FontScale;                  // Current/default font scale (== FontSize / Font->FontSize)
+    ImFontAtlas*    FontAtlas;                  // Current font atlas
+    ImFont*         Font;                       // Current font (used for simplified AddText overload)
+    float           FontSize;                   // Current font size (used for for simplified AddText overload)
+    float           FontScale;                  // Current font scale (== FontSize / Font->FontSize)
     float           CurveTessellationTol;       // Tessellation tolerance when using PathBezierCurveTo()
     float           CircleSegmentMaxError;      // Number of circle segments to use per pixel of radius for AddCircle() etc
     float           InitialFringeScale;         // Initial scale to apply to AA fringe