MultiSelect: BoxSelect: fixed using in frozen table. (#7821, #5143) + added Demo.

Amend 0b4a1a40

imgui_demo.cpp

@@ -3306,6 +3306,52 @@ static void ShowDemoWindowMultiSelect(DemoWindowData* demo_data)
             ImGui::TreePop();
         }
 
+        // Demonstrate using the clipper with BeginMultiSelect()/EndMultiSelect()
+        IMGUI_DEMO_MARKER("Widgets/Selection State/Multi-Select (in a table)");
+        if (ImGui::TreeNode("Multi-Select (in a table)"))
+        {
+            static ImGuiSelectionBasicStorage selection;
+
+            const int ITEMS_COUNT = 10000;
+            ImGui::Text("Selection: %d/%d", selection.Size, ITEMS_COUNT);
+            if (ImGui::BeginTable("##Basket", 2, ImGuiTableFlags_ScrollY | ImGuiTableFlags_RowBg | ImGuiTableFlags_BordersOuter))
+            {
+                ImGui::TableSetupColumn("Object");
+                ImGui::TableSetupColumn("Action");
+                ImGui::TableSetupScrollFreeze(0, 1);
+                ImGui::TableHeadersRow();
+
+                ImGuiMultiSelectFlags flags = ImGuiMultiSelectFlags_ClearOnEscape | ImGuiMultiSelectFlags_BoxSelect1d;
+                ImGuiMultiSelectIO* ms_io = ImGui::BeginMultiSelect(flags, selection.Size, ITEMS_COUNT);
+                selection.ApplyRequests(ms_io);
+
+                ImGuiListClipper clipper;
+                clipper.Begin(ITEMS_COUNT);
+                if (ms_io->RangeSrcItem != -1)
+                    clipper.IncludeItemByIndex((int)ms_io->RangeSrcItem); // Ensure RangeSrc item is not clipped.
+                while (clipper.Step())
+                {
+                    for (int n = clipper.DisplayStart; n < clipper.DisplayEnd; n++)
+                    {
+                        ImGui::TableNextRow();
+                        ImGui::TableNextColumn();
+                        char label[64];
+                        sprintf(label, "Object %05d: %s", n, ExampleNames[n % IM_ARRAYSIZE(ExampleNames)]);
+                        bool item_is_selected = selection.Contains((ImGuiID)n);
+                        ImGui::SetNextItemSelectionUserData(n);
+                        ImGui::Selectable(label, item_is_selected, ImGuiSelectableFlags_SpanAllColumns | ImGuiSelectableFlags_AllowOverlap);
+                        ImGui::TableNextColumn();
+                        ImGui::SmallButton("hello");
+                    }
+                }
+
+                ms_io = ImGui::EndMultiSelect();
+                selection.ApplyRequests(ms_io);
+                ImGui::EndTable();
+            }
+            ImGui::TreePop();
+        }
+
         IMGUI_DEMO_MARKER("Widgets/Selection State/Multi-Select (checkboxes)");
         if (ImGui::TreeNode("Multi-Select (checkboxes)"))
         {

imgui_internal.h

@@ -3397,7 +3397,7 @@ namespace ImGui
     IMGUI_API int           TypingSelectFindBestLeadingMatch(ImGuiTypingSelectRequest* req, int items_count, const char* (*get_item_name_func)(void*, int), void* user_data);
 
     // Box-Select API
-    IMGUI_API bool          BeginBoxSelect(ImGuiWindow* window, ImGuiID box_select_id, ImGuiMultiSelectFlags ms_flags);
+    IMGUI_API bool          BeginBoxSelect(const ImRect& scope_rect, ImGuiWindow* window, ImGuiID box_select_id, ImGuiMultiSelectFlags ms_flags);
     IMGUI_API void          EndBoxSelect(const ImRect& scope_rect, ImGuiMultiSelectFlags ms_flags);
 
     // Multi-Select API

imgui_widgets.cpp

@@ -7221,7 +7221,7 @@ static void BoxSelectScrollWithMouseDrag(ImGuiBoxSelectState* bs, ImGuiWindow* w
     }
 }
 
-bool ImGui::BeginBoxSelect(ImGuiWindow* window, ImGuiID box_select_id, ImGuiMultiSelectFlags ms_flags)
+bool ImGui::BeginBoxSelect(const ImRect& scope_rect, ImGuiWindow* window, ImGuiID box_select_id, ImGuiMultiSelectFlags ms_flags)
 {
     ImGuiContext& g = *GImGui;
     ImGuiBoxSelectState* bs = &g.BoxSelectState;
@@ -7241,11 +7241,10 @@ bool ImGui::BeginBoxSelect(ImGuiWindow* window, ImGuiID box_select_id, ImGuiMult
 
     // Current frame absolute prev/current rectangles are used to toggle selection.
     // They are derived from positions relative to scrolling space.
-    const ImRect scope_rect = window->InnerClipRect;
     ImVec2 start_pos_abs = WindowPosRelToAbs(window, bs->StartPosRel);
     ImVec2 prev_end_pos_abs = WindowPosRelToAbs(window, bs->EndPosRel); // Clamped already
     ImVec2 curr_end_pos_abs = g.IO.MousePos;
-    if (ms_flags & ImGuiMultiSelectFlags_ScopeWindow)  // Box-select scrolling only happens with ScopeWindow
+    if (ms_flags & ImGuiMultiSelectFlags_ScopeWindow) // Box-select scrolling only happens with ScopeWindow
         curr_end_pos_abs = ImClamp(curr_end_pos_abs, scope_rect.Min, scope_rect.Max);
     bs->BoxSelectRectPrev.Min = ImMin(start_pos_abs, prev_end_pos_abs);
     bs->BoxSelectRectPrev.Max = ImMax(start_pos_abs, prev_end_pos_abs);
@@ -7299,6 +7298,7 @@ void ImGui::EndBoxSelect(const ImRect& scope_rect, ImGuiMultiSelectFlags ms_flag
 // [SECTION] Widgets: Multi-Select support
 //-------------------------------------------------------------------------
 // - DebugLogMultiSelectRequests() [Internal]
+// - CalcScopeRect() [Internal]
 // - BeginMultiSelect()
 // - EndMultiSelect()
 // - SetNextItemSelectionUserData()
@@ -7317,6 +7317,22 @@ static void DebugLogMultiSelectRequests(const char* function, const ImGuiMultiSe
     }
 }
 
+static ImRect CalcScopeRect(ImGuiMultiSelectTempData* ms, ImGuiWindow* window)
+{
+    if (ms->Flags & ImGuiMultiSelectFlags_ScopeRect)
+    {
+        // Warning: this depends on CursorMaxPos so it means to be called by EndMultiSelect() only
+        return ImRect(ms->ScopeRectMin, ImMax(window->DC.CursorMaxPos, ms->ScopeRectMin));
+    }
+    else
+    {
+        // Add inner table decoration (#7821) // FIXME: Why not baking in InnerClipRect?
+        ImRect scope_rect = window->InnerClipRect;
+        scope_rect.Min = ImMin(scope_rect.Min + ImVec2(window->DecoInnerSizeX1, window->DecoInnerSizeY1), scope_rect.Max);
+        return scope_rect;
+    }
+}
+
 // Return ImGuiMultiSelectIO structure.
 // Lifetime: don't hold on ImGuiMultiSelectIO* pointers over multiple frames or past any subsequent call to BeginMultiSelect() or EndMultiSelect().
 // Passing 'selection_size' and 'items_count' parameters is currently optional.
@@ -7399,7 +7415,7 @@ ImGuiMultiSelectIO* ImGui::BeginMultiSelect(ImGuiMultiSelectFlags flags, int sel
     if (flags & (ImGuiMultiSelectFlags_BoxSelect1d | ImGuiMultiSelectFlags_BoxSelect2d))
     {
         ms->BoxSelectId = GetID("##BoxSelect");
-        if (BeginBoxSelect(window, ms->BoxSelectId, flags))
+        if (BeginBoxSelect(CalcScopeRect(ms, window), window, ms->BoxSelectId, flags))
             request_clear |= bs->RequestClear;
     }
 
@@ -7452,7 +7468,7 @@ ImGuiMultiSelectIO* ImGui::EndMultiSelect()
     IM_ASSERT(g.CurrentMultiSelect != NULL && storage->Window == g.CurrentWindow);
     IM_ASSERT(g.MultiSelectTempDataStacked > 0 && &g.MultiSelectTempData[g.MultiSelectTempDataStacked - 1] == g.CurrentMultiSelect);
 
-    const ImRect scope_rect = (ms->Flags & ImGuiMultiSelectFlags_ScopeRect) ? ImRect(ms->ScopeRectMin, ImMax(window->DC.CursorMaxPos, ms->ScopeRectMin)) : window->InnerClipRect;
+    ImRect scope_rect = CalcScopeRect(ms, window);
     if (ms->IsFocused)
     {
         // We currently don't allow user code to modify RangeSrcItem by writing to BeginIO's version, but that would be an easy change here.