Multi-Select: Box-Select: improve dirty unclip rectangle calculation + use in ImGuiMultiSelectFlags_BoxSelect1d mode when needed (e.g. wheel scrolling up). (#7994, #8250, #7821, #7850, #7970)

docs/CHANGELOG.txt

@@ -61,6 +61,10 @@ Other Changes:
 - Multi-Select:
   - Fixed an issue using Multi-Select within a Table causing column width measurement to
     be invalid when trailing column contents is not submitted in the last row. (#9341, #8250)
+  - Box-Select: fixed an issue using ImGuiMultiSelectFlags_BoxSelect1d mode while scrolling.
+    Notably, using mouse wheel while holding a box-selection could lead items close to windows
+    edges from not being correctly unselected. (#7994, #8250, #7821, #7850, #7970)
+  - Box-Select: improved dirty/unclip rectangle logic for ImGuiMultiSelectFlags_BoxSelect2d.
   - Box-Select: fixed an issue using ImGuiMultiSelectFlags_BoxSelect2d mode, where
     items out of view wouldn't be properly selected while scrolling while mouse cursor
     is hovering outside of selection scope. (#7994, #1861, #6518)

imgui_internal.h

@@ -606,6 +606,8 @@ struct IMGUI_API ImRect
     bool        Overlaps(const ImRect& r) const     { return r.Min.y <  Max.y && r.Max.y >  Min.y && r.Min.x <  Max.x && r.Max.x >  Min.x; }
     void        Add(const ImVec2& p)                { if (Min.x > p.x)     Min.x = p.x;     if (Min.y > p.y)     Min.y = p.y;     if (Max.x < p.x)     Max.x = p.x;     if (Max.y < p.y)     Max.y = p.y; }
     void        Add(const ImRect& r)                { if (Min.x > r.Min.x) Min.x = r.Min.x; if (Min.y > r.Min.y) Min.y = r.Min.y; if (Max.x < r.Max.x) Max.x = r.Max.x; if (Max.y < r.Max.y) Max.y = r.Max.y; }
+    void        AddX(float x)                       { if (Min.x > x)       Min.x = x;       if (Max.x < x)       Max.x = x; }
+    void        AddY(float y)                       { if (Min.y > y)       Min.y = y;       if (Max.y < y)       Max.y = y; }
     void        Expand(const float amount)          { Min.x -= amount;   Min.y -= amount;   Max.x += amount;   Max.y += amount; }
     void        Expand(const ImVec2& amount)        { Min.x -= amount.x; Min.y -= amount.y; Max.x += amount.x; Max.y += amount.y; }
     void        Translate(const ImVec2& d)          { Min.x += d.x; Min.y += d.y; Max.x += d.x; Max.y += d.y; }
@@ -1893,6 +1895,7 @@ struct ImGuiBoxSelectState
     // Temporary/Transient data
     bool                    UnclipMode;         // (Temp/Transient, here in hot area). Set/cleared by the BeginMultiSelect()/EndMultiSelect() owning active box-select.
     ImRect                  UnclipRect;         // Rectangle where ItemAdd() clipping may be temporarily disabled. Need support by multi-select supporting widgets.
+    ImRect                  UnclipRects[2];     // Per-axis versions.
     ImRect                  BoxSelectRectPrev;  // Selection rectangle in absolute coordinates (derived every frame from BoxSelectStartPosRel and MousePos)
     ImRect                  BoxSelectRectCurr;
 

imgui_tables.cpp

@@ -1330,6 +1330,8 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
 // When starting a BeginMultiSelect() after table has been layout we update IsRequestOutput fields.
 void ImGui::TableApplyExternalUnclipRect(ImGuiTable* table, ImRect& rect)
 {
+    if (rect.IsInverted())
+        return;
     for (int column_n = 0; column_n < table->ColumnsCount; column_n++)
     {
         ImGuiTableColumn* column = &table->Columns[column_n];

imgui_widgets.cpp

@@ -7508,8 +7508,7 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
         RenderTextClipped(pos, ImVec2(ImMin(pos.x + size.x, window->WorkRect.Max.x), pos.y + size.y), label, label_end, &label_size, style.SelectableTextAlign, &bb);
 
 #ifdef IMGUI_DEBUG_BOXSELECT
-    if (g.BoxSelectState.UnclipMode)
+    if (g.BoxSelectState.UnclipMode) { GetForegroundDrawList()->AddText(pos, IM_COL32(255,255,0,200), label, label_end); }
-        GetForegroundDrawList()->AddText(pos, IM_COL32(255,255,0,200), label);
 #endif
 
     // Automatically close popups
@@ -7827,7 +7826,7 @@ bool ImGui::BeginBoxSelect(const ImRect& scope_rect, ImGuiWindow* window, ImGuiI
         return false;
 
     // Current frame absolute prev/current rectangles are used to toggle selection.
-    // They are derived from positions relative to scrolling space.
+    // They are derived from positions relative to scrolling space, so "previous" rectangle is reprojected for current frame coordinates.
     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;
@@ -7837,26 +7836,68 @@ bool ImGui::BeginBoxSelect(const ImRect& scope_rect, ImGuiWindow* window, ImGuiI
     bs->BoxSelectRectPrev.Max = ImMax(start_pos_abs, prev_end_pos_abs);
     bs->BoxSelectRectCurr.Min = ImMin(start_pos_abs, curr_end_pos_abs);
     bs->BoxSelectRectCurr.Max = ImMax(start_pos_abs, curr_end_pos_abs);
+    //IMGUI_DEBUG_LOG("StartPosRel (%.2f,%.2f) EndPosRel (%.2f,%.2f) -> (%.2f,%.2f)\n", bs->StartPosRel.x, bs->StartPosRel.y, bs->EndPosRel.x, bs->EndPosRel.y, WindowPosAbsToRel(window, g.IO.MousePos).x, WindowPosAbsToRel(window, g.IO.MousePos).y);
 
     // Box-select 2D mode detects change of the rectangle.
-    // Storing unclip rect used by widgets supporting box-select.
+    // Storing unclip rects which will be tested by widgets supporting box-select. Always update rectangles when active (even if we don't use them).
-    if (ms_flags & ImGuiMultiSelectFlags_BoxSelect2d)
+    // To facilitate understanding this: enable IMGUI_DEBUG_BOXSELECT and visualize all geometry.
+    if (ms_flags & (ImGuiMultiSelectFlags_BoxSelect1d | ImGuiMultiSelectFlags_BoxSelect2d))
     {
-        if (bs->BoxSelectRectPrev.Min != bs->BoxSelectRectCurr.Min || bs->BoxSelectRectPrev.Max != bs->BoxSelectRectCurr.Max)
+        // For both sides, compute the area differing between Prev and Curr rectangles.
-            bs->UnclipMode = true;
+        bs->UnclipRects[0] = bs->UnclipRects[1] = ImRect(+FLT_MAX, +FLT_MAX, -FLT_MAX, -FLT_MAX);
+        for (int side = 0; side < 2; side++)
+        {
+            ImVec2 d_min = (side == 0) ? ImMin(bs->BoxSelectRectCurr.Min, bs->BoxSelectRectPrev.Min) : ImMin(bs->BoxSelectRectCurr.Max, bs->BoxSelectRectPrev.Max);
+            ImVec2 d_max = (side == 0) ? ImMax(bs->BoxSelectRectCurr.Min, bs->BoxSelectRectPrev.Min) : ImMax(bs->BoxSelectRectCurr.Max, bs->BoxSelectRectPrev.Max);
+            if (d_min.x != d_max.x)
+            {
+                bs->UnclipRects[0].AddX(d_min.x);
+                bs->UnclipRects[0].AddX(d_max.x);
+            }
+            if (d_min.y != d_max.y)
+            {
+                bs->UnclipRects[1].AddY(d_min.y);
+                bs->UnclipRects[1].AddY(d_max.y);
+            }
+        }
 
-        // Always update rect even if we don't use it.
+        ImRect box_select_intersection = bs->BoxSelectRectPrev;
-        bs->UnclipRect = bs->BoxSelectRectPrev; // FIXME-OPT: UnclipRect X coordinates could be intersection of Prev and Curr rect on X axis.
+        box_select_intersection.Add(bs->BoxSelectRectCurr);
-        bs->UnclipRect.Add(bs->BoxSelectRectCurr);
+        if (ms_flags & ImGuiMultiSelectFlags_BoxSelect2d)
+            if (bs->BoxSelectRectPrev.Min.x != bs->BoxSelectRectCurr.Min.x || bs->BoxSelectRectPrev.Max.x != bs->BoxSelectRectCurr.Max.x)
+            {
+                bs->UnclipRects[0].AddY(box_select_intersection.Min.y);
+                bs->UnclipRects[0].AddY(box_select_intersection.Max.y);
+            }
+        if (ms_flags & (ImGuiMultiSelectFlags_BoxSelect1d | ImGuiMultiSelectFlags_BoxSelect2d))
+            if (bs->BoxSelectRectPrev.Min.y != bs->BoxSelectRectCurr.Min.y || bs->BoxSelectRectPrev.Max.y != bs->BoxSelectRectCurr.Max.y)
+            {
+                bs->UnclipRects[1].AddX(box_select_intersection.Min.x);
+                bs->UnclipRects[1].AddX(box_select_intersection.Max.x);
+            }
+
+        // Merge both rectangles into one.
+        // FIXME-OPT: When UnclipRect.Area() is much larger than the sum of UnclipRects[0]/[1] Areas, widgets should
+        // ideally first use UnclipRect as a first coarse cull layer + the individual ones as a second validation.
+        bs->UnclipRect = bs->UnclipRects[0];
+        bs->UnclipRect.Add(bs->UnclipRects[1]);
+        if (!bs->UnclipRect.IsInverted() && (!window->ClipRect.Contains(bs->UnclipRect.Min) || !window->ClipRect.Contains(bs->UnclipRect.Max))) // !! Don't use Contains(ImRect)
+            bs->UnclipMode = true;
+        if (bs->UnclipMode && g.CurrentTable != NULL)
+            TableApplyExternalUnclipRect(g.CurrentTable, bs->UnclipRect); // No need submitting both
     }
-    if (bs->UnclipMode && g.CurrentTable != NULL)
-        TableApplyExternalUnclipRect(g.CurrentTable, bs->UnclipRect);
 
 #ifdef IMGUI_DEBUG_BOXSELECT
-    if (ms_flags & ImGuiMultiSelectFlags_BoxSelect2d)
+    //GetForegroundDrawList()->AddRect(scope_rect.Min, scope_rect.Max, IM_COL32(0, 255, 0, 200), 0.0f, 0, 4.0f);
-        GetForegroundDrawList()->AddRect(bs->UnclipRect.Min, bs->UnclipRect.Max, bs->UnclipMode ? IM_COL32(255,255,0,200) : IM_COL32(255,0,0,200), 0.0f, 0, 4.0f);
     //GetForegroundDrawList()->AddRect(bs->BoxSelectRectPrev.Min, bs->BoxSelectRectPrev.Max, IM_COL32(255,0,0,200), 0.0f, 0, 3.0f);
     //GetForegroundDrawList()->AddRect(bs->BoxSelectRectCurr.Min, bs->BoxSelectRectCurr.Max, IM_COL32(0,255,0,200), 0.0f, 0, 1.0f);
+    if (ms_flags & (ImGuiMultiSelectFlags_BoxSelect1d | ImGuiMultiSelectFlags_BoxSelect2d))
+    {
+        for (ImRect& unclip_r : bs->UnclipRects)
+            if (!unclip_r.IsInverted())
+                GetForegroundDrawList()->AddRect(unclip_r.Min, unclip_r.Max, bs->UnclipMode ? IM_COL32(255, 255, 0, 200) : IM_COL32(255, 0, 0, 200), 0.0f, 0, 4.0f);
+        GetForegroundDrawList()->AddRect(bs->UnclipRect.Min, bs->UnclipRect.Max, bs->UnclipMode ? IM_COL32(255, 255, 0, 200) : IM_COL32(255, 0, 0, 200), 0.0f, 0, 2.0f);
+    }
 #endif
     return true;
 }