Tables: added TableGetHoveredRow() in imgui_internal.h. (#6250, #6347, #6588, #3740)

Works with one-frame delay inconsistent with other functions, may be too bug-prone.

imgui_internal.h

@@ -2573,8 +2573,10 @@ struct ImGuiTableInstanceData
     float                       LastOuterHeight;            // Outer height from last frame
     float                       LastFirstRowHeight;         // Height of first row from last frame (FIXME: this is used as "header height" and may be reworked)
     float                       LastFrozenHeight;           // Height of frozen section from last frame
+    int                         HoveredRowLast;             // Index of row which was hovered last frame.
+    int                         HoveredRowNext;             // Index of row hovered this frame, set after encountering it.
 
-    ImGuiTableInstanceData()    { TableInstanceID = 0; LastOuterHeight = LastFirstRowHeight = LastFrozenHeight = 0.0f; }
+    ImGuiTableInstanceData()    { TableInstanceID = 0; LastOuterHeight = LastFirstRowHeight = LastFrozenHeight = 0.0f; HoveredRowLast = HoveredRowNext = -1; }
 };
 
 // FIXME-TABLE: more transient data could be stored in a stacked ImGuiTableTempData: e.g. SortSpecs, incoming RowData
@@ -3056,7 +3058,8 @@ namespace ImGui
     IMGUI_API void          TableOpenContextMenu(int column_n = -1);
     IMGUI_API void          TableSetColumnWidth(int column_n, float width);
     IMGUI_API void          TableSetColumnSortDirection(int column_n, ImGuiSortDirection sort_direction, bool append_to_sort_specs);
-    IMGUI_API int           TableGetHoveredColumn(); // May use (TableGetColumnFlags() & ImGuiTableColumnFlags_IsHovered) instead. Return hovered column. return -1 when table is not hovered. return columns_count if the unused space at the right of visible columns is hovered.
+    IMGUI_API int           TableGetHoveredColumn();    // May use (TableGetColumnFlags() & ImGuiTableColumnFlags_IsHovered) instead. Return hovered column. return -1 when table is not hovered. return columns_count if the unused space at the right of visible columns is hovered.
+    IMGUI_API int           TableGetHoveredRow();       // Retrieve *PREVIOUS FRAME* hovered row. This difference with TableGetHoveredColumn() is the reason why this is not public yet.
     IMGUI_API float         TableGetHeaderRowHeight();
     IMGUI_API void          TablePushBackgroundChannel();
     IMGUI_API void          TablePopBackgroundChannel();

imgui_tables.cpp

@@ -967,6 +967,8 @@ void ImGui::TableUpdateLayout(ImGuiTable* table)
     //   clear ActiveId, which is equivalent to the change provided by _AllowWhenBLockedByActiveItem).
     // - This allows columns to be marked as hovered when e.g. clicking a button inside the column, or using drag and drop.
     ImGuiTableInstanceData* table_instance = TableGetInstanceData(table, table->InstanceCurrent);
+    table_instance->HoveredRowLast = table_instance->HoveredRowNext;
+    table_instance->HoveredRowNext = -1;
     table->HoveredColumnBody = -1;
     table->HoveredColumnBorder = -1;
     const ImRect mouse_hit_rect(table->OuterRect.Min.x, table->OuterRect.Min.y, table->OuterRect.Max.x, ImMax(table->OuterRect.Max.y, table->OuterRect.Min.y + table_instance->LastOuterHeight));
@@ -1543,6 +1545,7 @@ void ImGui::TableSetupScrollFreeze(int columns, int rows)
 // - TableGetCellBgRect() [Internal]
 // - TableGetColumnResizeID() [Internal]
 // - TableGetHoveredColumn() [Internal]
+// - TableGetHoveredRow() [Internal]
 // - TableSetBgColor()
 //-----------------------------------------------------------------------------
 
@@ -1647,6 +1650,19 @@ int ImGui::TableGetHoveredColumn()
     return (int)table->HoveredColumnBody;
 }
 
+// Return -1 when table is not hovered. Return maxrow+1 if in table but below last submitted row.
+// *IMPORTANT* Unlike TableGetHoveredColumn(), this has a one frame latency in updating the value.
+// This difference with is the reason why this is not public yet.
+int ImGui::TableGetHoveredRow()
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiTable* table = g.CurrentTable;
+    if (!table)
+        return -1;
+    ImGuiTableInstanceData* table_instance = TableGetInstanceData(table, table->InstanceCurrent);
+    return (int)table_instance->HoveredRowLast;
+}
+
 void ImGui::TableSetBgColor(ImGuiTableBgTarget target, ImU32 color, int column_n)
 {
     ImGuiContext& g = *GImGui;
@@ -1798,6 +1814,10 @@ void ImGui::TableEndRow(ImGuiTable* table)
     const bool is_visible = (bg_y2 >= table->InnerClipRect.Min.y && bg_y1 <= table->InnerClipRect.Max.y);
     if (is_visible)
     {
+        // Update data for TableGetHoveredRow()
+        if (table->HoveredColumnBody != -1 && g.IO.MousePos.y >= bg_y1 && g.IO.MousePos.y < bg_y2)
+            TableGetInstanceData(table, table->InstanceCurrent)->HoveredRowNext = table->CurrentRow;
+
         // Decide of background color for the row
         ImU32 bg_col0 = 0;
         ImU32 bg_col1 = 0;
@@ -3591,6 +3611,11 @@ void ImGui::DebugNodeTable(ImGuiTable* table)
     BulletText("CellPaddingX: %.1f, CellSpacingX: %.1f/%.1f, OuterPaddingX: %.1f", table->CellPaddingX, table->CellSpacingX1, table->CellSpacingX2, table->OuterPaddingX);
     BulletText("HoveredColumnBody: %d, HoveredColumnBorder: %d", table->HoveredColumnBody, table->HoveredColumnBorder);
     BulletText("ResizedColumn: %d, ReorderColumn: %d, HeldHeaderColumn: %d", table->ResizedColumn, table->ReorderColumn, table->HeldHeaderColumn);
+    for (int n = 0; n < table->InstanceCurrent + 1; n++)
+    {
+        ImGuiTableInstanceData* table_instance = TableGetInstanceData(table, n);
+        BulletText("Instance %d: HoveredRow: %d, LastOuterHeight: %.2f", n, table_instance->HoveredRowLast, table_instance->LastOuterHeight);
+    }
     //BulletText("BgDrawChannels: %d/%d", 0, table->BgDrawChannelUnfrozen);
     float sum_weights = 0.0f;
     for (int n = 0; n < table->ColumnsCount; n++)