Clipper, Tables: added ImGuiListClipperFlags, ImGuiListClipperFlags_NoSetTableRowCounters. (#8886)

a0cdac48e0 revealed the issue but technically the core issue is that clipper assume 1 item = 1 table row.

docs/CHANGELOG.txt

@@ -47,6 +47,9 @@ Other Changes:
   ImGuiStyleVar_ScrollbarPadding enum, instead of hardcoded computed default. (#8895)
 - Fonts: fixed an assertion failure when a rectangle entry has been reused
   1024 times (e.g. due to constant change of font types). (#8906) [@cfillion]
+- Clipper, Tables: added ImGuiListClipperFlags_NoSetTableRowCounters as a way to
+  disable the assumption that 1 clipper item == 1 table row, which breaks when
+  e.g. using clipper with ItemsHeight=1 in order to clip in pixel units. (#8886)
 - Fixed Bullet() fixed tesselation amount which looked out of place in very large sizes.
 - DrawList: Fixed CloneOutput() unnecessarily taking a copy of the ImDrawListSharedData
   pointer, which could to issue when deleting the cloned list. (#8894, #1860)

imgui.cpp

@@ -3124,7 +3124,7 @@ static void ImGuiListClipper_SortAndFuseRanges(ImVector<ImGuiListClipperRange>&
     }
 }
 
-static void ImGuiListClipper_SeekCursorAndSetupPrevLine(float pos_y, float line_height)
+static void ImGuiListClipper_SeekCursorAndSetupPrevLine(ImGuiListClipper* clipper, float pos_y, float line_height)
 {
     // Set cursor position and a few other things so that SetScrollHereY() and Columns() can work when seeking cursor.
     // FIXME: It is problematic that we have to do that here, because custom/equivalent end-user code would stumble on the same issue.
@@ -3142,10 +3142,14 @@ static void ImGuiListClipper_SeekCursorAndSetupPrevLine(float pos_y, float line_
     {
         if (table->IsInsideRow)
             ImGui::TableEndRow(table);
+        if ((clipper->Flags & ImGuiListClipperFlags_NoSetTableRowCounters) == 0)
+        {
+            const int row_increase = (int)((off_y / line_height) + 0.5f);
+            IM_ASSERT(row_increase >= 0); // If your clipper item height is != from actual table row height, consider using ImGuiListClipperFlags_NoSetTableRowCounters. See #8886.
+            table->CurrentRow += row_increase;
+            table->RowBgColorCounter += row_increase;
+        }
         table->RowPosY2 = window->DC.CursorPos.y;
-        const int row_increase = (int)((off_y / line_height) + 0.5f);
-        table->CurrentRow += row_increase;
-        table->RowBgColorCounter += row_increase;
     }
 }
 
@@ -3228,7 +3232,7 @@ void ImGuiListClipper::SeekCursorForItem(int item_n)
     // - StartPosY starts from ItemsFrozen, by adding SeekOffsetY we generally cancel that out (SeekOffsetY == LossynessOffset - ItemsFrozen * ItemsHeight).
     // - The reason we store SeekOffsetY instead of inferring it, is because we want to allow user to perform Seek after the last step, where ImGuiListClipperData is already done.
     float pos_y = (float)((double)StartPosY + StartSeekOffsetY + (double)item_n * ItemsHeight);
-    ImGuiListClipper_SeekCursorAndSetupPrevLine(pos_y, ItemsHeight);
+    ImGuiListClipper_SeekCursorAndSetupPrevLine(this, pos_y, ItemsHeight);
 }
 
 static bool ImGuiListClipper_StepInternal(ImGuiListClipper* clipper)
@@ -3327,7 +3331,6 @@ static bool ImGuiListClipper_StepInternal(ImGuiListClipper* clipper)
             if (g.NavId != 0 && window->NavLastIds[0] == g.NavId)
                 data->Ranges.push_back(ImGuiListClipperRange::FromPositions(nav_rect_abs.Min.y, nav_rect_abs.Max.y, 0, 0));
 
-            // Add visible range
             float min_y = window->ClipRect.Min.y;
             float max_y = window->ClipRect.Max.y;
 
@@ -3346,6 +3349,7 @@ static bool ImGuiListClipper_StepInternal(ImGuiListClipper* clipper)
                     data->Ranges.push_back(ImGuiListClipperRange::FromPositions(bs->UnclipRect.Min.y, bs->UnclipRect.Max.y, 0, 0));
             }
 
+            // Add main visible range
             const int off_min = (is_nav_request && g.NavMoveClipDir == ImGuiDir_Up) ? -1 : 0;
             const int off_max = (is_nav_request && g.NavMoveClipDir == ImGuiDir_Down) ? 1 : 0;
             data->Ranges.push_back(ImGuiListClipperRange::FromPositions(min_y, max_y, off_min, off_max));

imgui.h

@@ -29,7 +29,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.92.3 WIP"
-#define IMGUI_VERSION_NUM   19223
+#define IMGUI_VERSION_NUM   19224
 #define IMGUI_HAS_TABLE             // Added BeginTable() - from IMGUI_VERSION_NUM >= 18000
 #define IMGUI_HAS_TEXTURES          // Added ImGuiBackendFlags_RendererHasTextures - from IMGUI_VERSION_NUM >= 19198
 
@@ -246,6 +246,7 @@ typedef int ImGuiInputFlags;        // -> enum ImGuiInputFlags_      // Flags: f
 typedef int ImGuiInputTextFlags;    // -> enum ImGuiInputTextFlags_  // Flags: for InputText(), InputTextMultiline()
 typedef int ImGuiItemFlags;         // -> enum ImGuiItemFlags_       // Flags: for PushItemFlag(), shared by all items
 typedef int ImGuiKeyChord;          // -> ImGuiKey | ImGuiMod_XXX    // Flags: for IsKeyChordPressed(), Shortcut() etc. an ImGuiKey optionally OR-ed with one or more ImGuiMod_XXX values.
+typedef int ImGuiListClipperFlags;  // -> enum ImGuiListClipperFlags_// Flags: for ImGuiListClipper
 typedef int ImGuiPopupFlags;        // -> enum ImGuiPopupFlags_      // Flags: for OpenPopup*(), BeginPopupContext*(), IsPopupOpen()
 typedef int ImGuiMultiSelectFlags;  // -> enum ImGuiMultiSelectFlags_// Flags: for BeginMultiSelect()
 typedef int ImGuiSelectableFlags;   // -> enum ImGuiSelectableFlags_ // Flags: for Selectable()
@@ -2782,6 +2783,13 @@ struct ImGuiStorage
 #endif
 };
 
+// Flags for ImGuiListClipper (currently not fully exposed in function calls: a future refactor will likely add this to ImGuiListClipper::Begin function equivalent)
+enum ImGuiListClipperFlags_
+{
+    ImGuiListClipperFlags_None                  = 0,
+    ImGuiListClipperFlags_NoSetTableRowCounters = 1 << 0,   // [Internal] Disabled modifying table row counters. Avoid assumption that 1 clipper item == 1 table row.
+};
+
 // Helper: Manually clip large list of items.
 // If you have lots evenly spaced items and you have random access to the list, you can perform coarse
 // clipping based on visibility to only submit items that are in view.
@@ -2812,6 +2820,7 @@ struct ImGuiListClipper
     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
+    ImGuiListClipperFlags Flags;        // [Internal] Flags, currently not yet well exposed.
 
     // items_count: Use INT_MAX if you don't know how many items you have (in which case the cursor won't be advanced in the final step, and you can call SeekCursorForItem() manually if you need)
     // items_height: Use -1.0f to be calculated automatically on first step. Otherwise pass in the distance between your items, typically GetTextLineHeightWithSpacing() or GetFrameHeightWithSpacing().

imgui_tables.cpp

@@ -2054,10 +2054,11 @@ void ImGui::TableEndRow(ImGuiTable* table)
     }
 
     // End frozen rows (when we are past the last frozen row line, teleport cursor and alter clipping rectangle)
-    // We need to do that in TableEndRow() instead of TableBeginRow() so the list clipper can mark end of row and
-    // get the new cursor position.
+    // - We need to do that in TableEndRow() instead of TableBeginRow() so the list clipper can mark
+    //   end of row and get the new cursor position.
     if (unfreeze_rows_request)
     {
+        IM_ASSERT(table->FreezeRowsRequest > 0);
         for (int column_n = 0; column_n < table->ColumnsCount; column_n++)
             table->Columns[column_n].NavLayerCurrent = table->NavLayer;
         const float y0 = ImMax(table->RowPosY2 + 1, table->InnerClipRect.Min.y);