Canvas: Remember index of first command buffer to not miss updating any used (#260)

Author: thedmd

docs/CHANGELOG.txt

@@ -1,6 +1,6 @@
 v0.9.4 (WIP):
 
-    nothing yet
+    BUGFIX: Canvas: Remember index of first command buffer to not miss updating any used (#260)
 
 v0.9.3 (2023-10-14):
 

imgui_canvas.cpp

@@ -445,6 +445,8 @@ void ImGuiEx::Canvas::EnterLocalSpace()
     if ((!m_DrawList->CmdBuffer.empty() && m_DrawList->CmdBuffer.back().ElemCount > 0) || m_DrawList->_Splitter._Count > 1)
         m_DrawList->AddCallback(ImDrawCallback_ImCanvas, nullptr);
 
+    m_DrawListFirstCommandIndex = ImMax(m_DrawList->CmdBuffer.Size - 1, 0);
+
 # if defined(IMGUI_HAS_VIEWPORT)
     auto window = ImGui::GetCurrentWindow();
     window->Pos = ImVec2(0.0f, 0.0f);
@@ -523,7 +525,7 @@ void ImGuiEx::Canvas::LeaveLocalSpace()
         }
 
         // Move clip rectangles to screen space.
-        for (int i = m_DrawListCommadBufferSize; i < m_DrawList->CmdBuffer.size(); ++i)
+        for (int i = m_DrawListFirstCommandIndex; i < m_DrawList->CmdBuffer.size(); ++i)
         {
             auto& command = m_DrawList->CmdBuffer[i];
             command.ClipRect.x = command.ClipRect.x * m_View.Scale + m_ViewTransformPosition.x;
@@ -542,7 +544,7 @@ void ImGuiEx::Canvas::LeaveLocalSpace()
         }
 
         // Move clip rectangles to screen space.
-        for (int i = m_DrawListCommadBufferSize; i < m_DrawList->CmdBuffer.size(); ++i)
+        for (int i = m_DrawListFirstCommandIndex; i < m_DrawList->CmdBuffer.size(); ++i)
         {
             auto& command = m_DrawList->CmdBuffer[i];
             command.ClipRect.x = command.ClipRect.x + m_ViewTransformPosition.x;

imgui_canvas.h

@@ -236,6 +236,7 @@ struct Canvas
     Range* m_CurrentRange = nullptr;
 # endif
 
+    int m_DrawListFirstCommandIndex = 0;
     int m_DrawListCommadBufferSize = 0;
     int m_DrawListStartVertexIndex = 0;