Clipper: further mitigation/improvements for abnormally large contents ranges (larger than e.g. 2^31). (#3609, #8215)

docs/CHANGELOG.txt

@@ -108,6 +108,7 @@ Other changes:
 - 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)
+- Clipper: some mitigation/improvements for 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

@@ -3195,10 +3195,17 @@ static bool ImGuiListClipper_StepInternal(ImGuiListClipper* clipper)
         if (table)
             IM_ASSERT(table->RowPosY1 == clipper->StartPosY && table->RowPosY2 == window->DC.CursorPos.y);
 
-        clipper->ItemsHeight = (window->DC.CursorPos.y - clipper->StartPosY) / (float)(clipper->DisplayEnd - clipper->DisplayStart);
-        bool affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(clipper->StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
+        bool affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision((float)clipper->StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
         if (affected_by_floating_point_precision)
+        {
+            // Mitigation/hack for very large range: assume last time height constitute line height.
             clipper->ItemsHeight = window->DC.PrevLineSize.y + g.Style.ItemSpacing.y; // FIXME: Technically wouldn't allow multi-line entries.
+            window->DC.CursorPos.y = (float)(clipper->StartPosY + clipper->ItemsHeight);
+        }
+        else
+        {
+            clipper->ItemsHeight = (float)(window->DC.CursorPos.y - clipper->StartPosY) / (float)(clipper->DisplayEnd - clipper->DisplayStart);
+        }
         if (clipper->ItemsHeight == 0.0f && clipper->ItemsCount == INT_MAX) // Accept that no item have been submitted if in indeterminate mode.
             return false;
         IM_ASSERT(clipper->ItemsHeight > 0.0f && "Unable to calculate item height! First item hasn't moved the cursor vertically!");

imgui.h

@@ -2708,7 +2708,7 @@ struct ImGuiListClipper
     int             DisplayEnd;         // End of items to display (exclusive)
     int             ItemsCount;         // [Internal] Number of items
     float           ItemsHeight;        // [Internal] Height of item after a first step and item submission can calculate it
-    float           StartPosY;          // [Internal] Cursor position at the time of Begin() or after table frozen rows are all processed
+    double          StartPosY;          // [Internal] Cursor position at the time of Begin() or after table frozen rows are all processed
     double          StartSeekOffsetY;   // [Internal] Account for frozen rows in a table and initial loss of precision in very large windows.
     void*           TempData;           // [Internal] Internal data