Clipper: use line size instead of cursor comparaison when range are large. (ocornut#3609, ocornut#3962 + ocornut/imgui_club#20)

Author: ocornut

Diff for: imgui.cpp

@@ -2471,17 +2471,23 @@ bool ImGuiListClipper::Step()
     if (ItemsHeight <= 0.0f)
     {
         IM_ASSERT(data->StepNo == 1);
+        bool affected_by_floating_point_precision = false;
         if (table)
         {
             const float pos_y1 = table->RowPosY1;   // Using RowPosY1 instead of StartPosY to handle clipper straddling the frozen row
             const float pos_y2 = table->RowPosY2;   // Using RowPosY2 instead of CursorPos.y to take account of tallest cell.
             ItemsHeight = pos_y2 - pos_y1;
             window->DC.CursorPos.y = pos_y2;
+            affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(pos_y1) || ImIsFloatAboveGuaranteedIntegerPrecision(pos_y2);
         }
         else
         {
             ItemsHeight = (window->DC.CursorPos.y - StartPosY) / (float)(DisplayEnd - DisplayStart);
+            affected_by_floating_point_precision = ImIsFloatAboveGuaranteedIntegerPrecision(StartPosY) || ImIsFloatAboveGuaranteedIntegerPrecision(window->DC.CursorPos.y);
         }
+        if (affected_by_floating_point_precision)
+            ItemsHeight = window->DC.PrevLineSize.y + g.Style.ItemSpacing.y; // FIXME: Technically wouldn't allow multi-line entries.
+
         IM_ASSERT(ItemsHeight > 0.0f && "Unable to calculate item height! First item hasn't moved the cursor vertically!");
         calc_clipping = true;   // If item height had to be calculated, calculate clipping afterwards.
     }

Diff for: imgui.h

@@ -64,7 +64,7 @@ Index of this file:
 // Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals. Work in progress versions typically starts at XYY99 then bounce up to XYY00, XYY01 etc. when release tagging happens)
 #define IMGUI_VERSION               "1.86 WIP"
-#define IMGUI_VERSION_NUM           18515
+#define IMGUI_VERSION_NUM           18516
 #define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert), sizeof(ImDrawIdx))
 #define IMGUI_HAS_TABLE
 

Diff for: imgui_internal.h

@@ -448,6 +448,7 @@ static inline float  ImDot(const ImVec2& a, const ImVec2& b)
 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); }
 static inline float  ImLinearSweep(float current, float target, float speed)    { if (current < target) return ImMin(current + speed, target); if (current > target) return ImMax(current - speed, target); return current; }
 static inline ImVec2 ImMul(const ImVec2& lhs, const ImVec2& rhs)                { return ImVec2(lhs.x * rhs.x, lhs.y * rhs.y); }
+static inline bool   ImIsFloatAboveGuaranteedIntegerPrecision(float f)          { return f <= -16777216 || f >= 16777216; }
 IM_MSVC_RUNTIME_CHECKS_RESTORE
 
 // Helpers: Geometry