MultiSelect: Box-Select +Tables: fix usage of box-selection columns with items straying out of columns. (#7994, #2221)

Use 00d3f9295e.
+ Assets Browser toggle to enable ScrollX.

docs/CHANGELOG.txt

@@ -83,6 +83,8 @@ Other Changes:
   - Box-Select: fixes for using accross nested child windows. (#8364)
   - Box-Select + Clipper: fixed an issue selecting items while scrolling while a clipper
     active. (#7994, #8250, #7821, #7850, #7970)
+  - Box-Select + Tables: fixed an issue using box-selection in a tables with
+    items straying out of columns boundaries. (#7994, #2221)
   - Box-Select + Tables: fixed an issue when calling `BeginMultiSelect()` in a table
     before layout has been locked (first row or headers row submitted). (#8250)
 - Style:

imgui_demo.cpp

@@ -10726,8 +10726,9 @@ struct ExampleAssetsBrowser
     bool            AllowDragUnselected = false;            // Will set ImGuiMultiSelectFlags_SelectOnClickRelease
     float           IconSize = 0;
     int             IconSpacing = 10;
-    int             IconHitSpacing = 4;         // Increase hit-spacing if you want to make it possible to clear or box-select from gaps. Some spacing is required to able to amend with Shift+box-select. Value is small in Explorer.
+    int             IconHitSpacing = 4;                     // Increase hit-spacing if you want to make it possible to clear or box-select from gaps. Some spacing is required to able to amend with Shift+box-select. Value is small in Explorer.
     bool            StretchSpacing = true;
+    bool            UseScrollX = false;                     // Debug: submit twice the number of items per line (overflow horizontally to exercise ScrollX + box-select)
 
     // State
     ImVector<ExampleAsset> Items;               // Our items
@@ -10778,12 +10779,15 @@ struct ExampleAssetsBrowser
         // Layout: calculate number of icon per line and number of lines
         LayoutItemSize = ImVec2(floorf(IconSize), floorf(IconSize));
         LayoutColumnCount = IM_MAX((int)(avail_width / (LayoutItemSize.x + LayoutItemSpacing)), 1);
-        LayoutLineCount = (Items.Size + LayoutColumnCount - 1) / LayoutColumnCount;
 
         // Layout: when stretching: allocate remaining space to more spacing. Round before division, so item_spacing may be non-integer.
         if (StretchSpacing && LayoutColumnCount > 1)
             LayoutItemSpacing = floorf(avail_width - LayoutItemSize.x * LayoutColumnCount) / LayoutColumnCount;
 
+        if (UseScrollX)
+            LayoutColumnCount *= 2;
+        LayoutLineCount = (Items.Size + LayoutColumnCount - 1) / LayoutColumnCount;
+
         LayoutItemStep = ImVec2(LayoutItemSize.x + LayoutItemSpacing, LayoutItemSize.y + LayoutItemSpacing);
         LayoutSelectableSpacing = IM_MAX(floorf(LayoutItemSpacing) - IconHitSpacing, 0.0f);
         LayoutOuterPadding = floorf(LayoutItemSpacing * 0.5f);
@@ -10843,6 +10847,7 @@ struct ExampleAssetsBrowser
                 ImGui::SliderInt("Icon Spacing", &IconSpacing, 0, 32);
                 ImGui::SliderInt("Icon Hit Spacing", &IconHitSpacing, 0, 32);
                 ImGui::Checkbox("Stretch Spacing", &StretchSpacing);
+                ImGui::Checkbox("Use ScrollX", &UseScrollX);
                 ImGui::PopItemWidth();
                 ImGui::EndMenu();
             }
@@ -10872,7 +10877,7 @@ struct ExampleAssetsBrowser
 
         ImGuiIO& io = ImGui::GetIO();
         ImGui::SetNextWindowContentSize(ImVec2(0.0f, LayoutOuterPadding + LayoutLineCount * (LayoutItemSize.y + LayoutItemSpacing)));
-        if (ImGui::BeginChild("Assets", ImVec2(0.0f, -ImGui::GetTextLineHeightWithSpacing()), ImGuiChildFlags_Borders, ImGuiWindowFlags_NoMove))
+        if (ImGui::BeginChild("Assets", ImVec2(0.0f, -ImGui::GetTextLineHeightWithSpacing()), ImGuiChildFlags_Borders, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_HorizontalScrollbar))
         {
             ImDrawList* draw_list = ImGui::GetWindowDrawList();
 

imgui_widgets.cpp

@@ -8358,8 +8358,15 @@ void ImGui::MultiSelectItemFooter(ImGuiID id, bool* p_selected, bool* p_pressed)
     if (ms->BoxSelectId != 0)
         if (ImGuiBoxSelectState* bs = GetBoxSelectState(ms->BoxSelectId))
         {
-            const bool rect_overlap_curr = bs->BoxSelectRectCurr.Overlaps(g.LastItemData.Rect);
+            ImRect item_rect = g.LastItemData.Rect;
-            const bool rect_overlap_prev = bs->BoxSelectRectPrev.Overlaps(g.LastItemData.Rect);
+            if (!window->DC.NavIsScrollPushableX)
+            {
+                const ImRect& clip_rect = (g.LastItemData.StatusFlags & ImGuiItemStatusFlags_HasClipRect) ? g.LastItemData.ClipRect : window->ClipRect;
+                item_rect.Min.x = ImMax(item_rect.Min.x, clip_rect.Min.x);
+                item_rect.Max.x = ImMin(item_rect.Max.x, clip_rect.Max.x);
+            }
+            const bool rect_overlap_curr = bs->BoxSelectRectCurr.Overlaps(item_rect);
+            const bool rect_overlap_prev = bs->BoxSelectRectPrev.Overlaps(item_rect);
             if ((rect_overlap_curr && !rect_overlap_prev && !selected) || (rect_overlap_prev && !rect_overlap_curr))
             {
                 if (storage->LastSelectionSize <= 0 && bs->IsStartedSetNavIdOnce)