Columns: Caching columns clipping rectangles (#125)

imgui.cpp

@@ -8607,7 +8607,7 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
     ImGuiContext& g = *GImGui;
     const ImGuiStyle& style = g.Style;
 
-    if ((flags & ImGuiSelectableFlags_SpanAllColumns) && window->DC.ColumnsCount > 1)
+    if ((flags & ImGuiSelectableFlags_SpanAllColumns) && window->DC.ColumnsCount > 1) // FIXME-OPT: Avoid if vertically clipped.
         PopClipRect();
 
     ImGuiID id = window->GetID(label);
@@ -10021,13 +10021,11 @@ void ImGui::SetColumnWidth(int column_index, float width)
 
 void ImGui::PushColumnClipRect(int column_index)
 {
-    ImGuiWindow* window = ImGui::GetCurrentWindow();
+    ImGuiWindow* window = GetCurrentWindowRead();
     if (column_index < 0)
         column_index = window->DC.ColumnsCurrent;
 
-    float x1 = ImFloor(0.5f + window->Pos.x + ImGui::GetColumnOffset(column_index) - 1.0f);
-    float x2 = ImFloor(0.5f + window->Pos.x + ImGui::GetColumnOffset(column_index+1) - 1.0f);
-    ImGui::PushClipRect(ImVec2(x1,-FLT_MAX), ImVec2(x2,+FLT_MAX), true);
+    PushClipRect(window->DC.ColumnsData[column_index].ClipRect.Min, window->DC.ColumnsData[column_index].ClipRect.Max, false);
 }
 
 void ImGui::BeginColumns(const char* id, int columns_count, ImGuiColumnsFlags flags)
@@ -10066,11 +10064,21 @@ void ImGui::BeginColumns(const char* id, int columns_count, ImGuiColumnsFlags fl
         const ImGuiID column_id = window->DC.ColumnsSetId + ImGuiID(column_index);
         KeepAliveID(column_id);
         const float default_t = column_index / (float)window->DC.ColumnsCount;
-        float t = window->DC.StateStorage->GetFloat(column_id, default_t);      // Cheaply store our floating point value inside the integer (could store a union into the map?)
+        float t = window->DC.StateStorage->GetFloat(column_id, default_t);
         if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoForceWithinWindow))
             t = ImMin(t, PixelsToOffsetNorm(window, window->DC.ColumnsMaxX - g.Style.ColumnsMinSpacing * (window->DC.ColumnsCount - column_index)));
         window->DC.ColumnsData[column_index].OffsetNorm = t;
     }
+
+    // Cache clipping rectangles
+    for (int column_index = 0; column_index < columns_count; column_index++)
+    {
+        float clip_x1 = ImFloor(0.5f + window->Pos.x + GetColumnOffset(column_index) - 1.0f);
+        float clip_x2 = ImFloor(0.5f + window->Pos.x + GetColumnOffset(column_index + 1) - 1.0f);
+        window->DC.ColumnsData[column_index].ClipRect = ImRect(clip_x1, -FLT_MAX, clip_x2, +FLT_MAX);
+        window->DC.ColumnsData[column_index].ClipRect.Clip(window->ClipRect);
+    }
+
     window->DrawList->ChannelsSplit(window->DC.ColumnsCount);
     PushColumnClipRect();
     PushItemWidth(GetColumnWidth() * 0.65f);

imgui_internal.h

@@ -316,6 +316,7 @@ struct ImGuiGroupData
 struct ImGuiColumnData
 {
     float       OffsetNorm; // Column start offset, normalized 0.0 (far left) -> 1.0 (far right)
+    ImRect      ClipRect;
     //float     IndentX;
 };