Scroll: fixed contents size, scrollbar visibility and scrolling reet issue with abnormally large contents ranges. (#3609, #8215)

docs/CHANGELOG.txt

@@ -106,6 +106,8 @@ Other changes:
   windows (e.g. determined programmatically) can lead to renderer backend trying to
   create abnormally large framebuffers.
 - TextLinkOpenURL(): added bool return value on click. (#8645, #8451, #7660)
+- Scroll: fixed contents size, scrollbar visibility and scrolling resetting issues
+  with abnormally large contents ranges. (#3609, #8215)
 - Nav: fixed assertion when holding gamepad FaceLeft/West button to open
   CTRL+Tab windowing + pressing a keyboard key. (#8525)
 - Error Handling: added better error report and recovery for extraneous

imgui.cpp

@@ -6390,10 +6390,10 @@ static void CalcWindowContentSizes(ImGuiWindow* window, ImVec2* content_size_cur
         return;
     }
 
-    content_size_current->x = (window->ContentSizeExplicit.x != 0.0f) ? window->ContentSizeExplicit.x : IM_TRUNC(window->DC.CursorMaxPos.x - window->DC.CursorStartPos.x);
-    content_size_current->y = (window->ContentSizeExplicit.y != 0.0f) ? window->ContentSizeExplicit.y : IM_TRUNC(window->DC.CursorMaxPos.y - window->DC.CursorStartPos.y);
-    content_size_ideal->x = (window->ContentSizeExplicit.x != 0.0f) ? window->ContentSizeExplicit.x : IM_TRUNC(ImMax(window->DC.CursorMaxPos.x, window->DC.IdealMaxPos.x) - window->DC.CursorStartPos.x);
-    content_size_ideal->y = (window->ContentSizeExplicit.y != 0.0f) ? window->ContentSizeExplicit.y : IM_TRUNC(ImMax(window->DC.CursorMaxPos.y, window->DC.IdealMaxPos.y) - window->DC.CursorStartPos.y);
+    content_size_current->x = (window->ContentSizeExplicit.x != 0.0f) ? window->ContentSizeExplicit.x : ImTrunc64(window->DC.CursorMaxPos.x - window->DC.CursorStartPos.x);
+    content_size_current->y = (window->ContentSizeExplicit.y != 0.0f) ? window->ContentSizeExplicit.y : ImTrunc64(window->DC.CursorMaxPos.y - window->DC.CursorStartPos.y);
+    content_size_ideal->x = (window->ContentSizeExplicit.x != 0.0f) ? window->ContentSizeExplicit.x : ImTrunc64(ImMax(window->DC.CursorMaxPos.x, window->DC.IdealMaxPos.x) - window->DC.CursorStartPos.x);
+    content_size_ideal->y = (window->ContentSizeExplicit.y != 0.0f) ? window->ContentSizeExplicit.y : ImTrunc64(ImMax(window->DC.CursorMaxPos.y, window->DC.IdealMaxPos.y) - window->DC.CursorStartPos.y);
 }
 
 static ImVec2 CalcWindowAutoFitSize(ImGuiWindow* window, const ImVec2& size_contents)
@@ -11166,7 +11166,7 @@ static ImVec2 CalcNextScrollFromScrollTargetAndClamp(ImGuiWindow* window)
             }
             scroll[axis] = scroll_target - center_ratio * (window->SizeFull[axis] - decoration_size[axis]);
         }
-        scroll[axis] = IM_ROUND(ImMax(scroll[axis], 0.0f));
+        scroll[axis] = ImRound64(ImMax(scroll[axis], 0.0f));
         if (!window->Collapsed && !window->SkipItems)
             scroll[axis] = ImMin(scroll[axis], window->ScrollMax[axis]);
     }

imgui_internal.h

@@ -496,6 +496,8 @@ static inline float  ImTrunc(float f)
 static inline ImVec2 ImTrunc(const ImVec2& v)                                   { return ImVec2((float)(int)(v.x), (float)(int)(v.y)); }
 static inline float  ImFloor(float f)                                           { return (float)((f >= 0 || (float)(int)f == f) ? (int)f : (int)f - 1); } // Decent replacement for floorf()
 static inline ImVec2 ImFloor(const ImVec2& v)                                   { return ImVec2(ImFloor(v.x), ImFloor(v.y)); }
+static inline float  ImTrunc64(float f)                                         { return (float)(ImS64)(f); }
+static inline float  ImRound64(float f)                                         { return (float)(ImS64)(f + 0.5f); }
 static inline int    ImModPositive(int a, int b)                                { return (a + b) % b; }
 static inline float  ImDot(const ImVec2& a, const ImVec2& b)                    { return a.x * b.x + a.y * b.y; }
 static inline ImVec2 ImRotate(const ImVec2& v, float cos_a, float sin_a)        { return ImVec2(v.x * cos_a - v.y * sin_a, v.x * sin_a + v.y * cos_a); }