Began improvements to columns API by splitting the Columns() function into BeginColumns() and EndColumns() and adding additional flags. The columns data still needs to be placed into a stack.

imgui.cpp

@@ -9295,6 +9295,18 @@ int ImGui::GetColumnsCount()
     return window->DC.ColumnsCount;
 }
 
+static float OffsetNormToPixels(float offsetNorm)
+{
+    ImGuiWindow* window = ImGui::GetCurrentWindowRead();
+    return offsetNorm * (window->DC.ColumnsMaxX - window->DC.ColumnsMinX);
+}
+
+static float PixelsToOffsetNorm(float offset)
+{
+    ImGuiWindow* window = ImGui::GetCurrentWindowRead();
+    return (offset - window->DC.ColumnsMinX) / (window->DC.ColumnsMaxX - window->DC.ColumnsMinX);
+}
+
 static float GetDraggedColumnOffset(int column_index)
 {
     // Active (dragged) column always follow mouse. The reason we need this is that dragging a column to the right edge of an auto-resizing
@@ -9305,7 +9317,9 @@ static float GetDraggedColumnOffset(int column_index)
     IM_ASSERT(g.ActiveId == window->DC.ColumnsSetId + ImGuiID(column_index));
 
     float x = g.IO.MousePos.x - g.ActiveIdClickOffset.x - window->Pos.x;
-    x = ImClamp(x, ImGui::GetColumnOffset(column_index-1)+g.Style.ColumnsMinSpacing, ImGui::GetColumnOffset(column_index+1)-g.Style.ColumnsMinSpacing);
+    x = ImMax(x, ImGui::GetColumnOffset(column_index-1) + g.Style.ColumnsMinSpacing);
+    if ((window->DC.ColumnsFlags & ImGuiColumnsFlags_NoPreserveWidths))
+        x = ImMin(x, ImGui::GetColumnOffset(column_index+1) - g.Style.ColumnsMinSpacing);
 
     return (float)(int)x;
 }
@@ -9332,16 +9346,26 @@ float ImGui::GetColumnOffset(int column_index)
 
 void ImGui::SetColumnOffset(int column_index, float offset)
 {
+    ImGuiContext& g = *GImGui;
     ImGuiWindow* window = GetCurrentWindow();
     if (column_index < 0)
         column_index = window->DC.ColumnsCurrent;
 
     IM_ASSERT(column_index < window->DC.ColumnsData.Size);
-    const float t = (offset - window->DC.ColumnsMinX) / (window->DC.ColumnsMaxX - window->DC.ColumnsMinX);
+
-    window->DC.ColumnsData[column_index].OffsetNorm = t;
+    const bool preserveWidth = !(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoPreserveWidths) && (column_index < window->DC.ColumnsCount-1);
+    const float width = preserveWidth ? GetColumnWidth(column_index) : 0.0f;
+
+    if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoForceWithinWindow))
+        offset = ImMin((float)(int)offset, window->DC.ColumnsMaxX - g.Style.ColumnsMinSpacing * (window->DC.ColumnsCount - column_index));
+    const float offsetNorm = PixelsToOffsetNorm(offset);
 
     const ImGuiID column_id = window->DC.ColumnsSetId + ImGuiID(column_index);
-    window->DC.StateStorage->SetFloat(column_id, t);
+    window->DC.StateStorage->SetFloat(column_id, offsetNorm);
+    window->DC.ColumnsData[column_index].OffsetNorm = offsetNorm;
+
+    if (preserveWidth)
+        SetColumnOffset(column_index+1, offset + ImMax(g.Style.ColumnsMinSpacing, width));
 }
 
 float ImGui::GetColumnWidth(int column_index)
@@ -9350,8 +9374,16 @@ float ImGui::GetColumnWidth(int column_index)
     if (column_index < 0)
         column_index = window->DC.ColumnsCurrent;
 
-    float w = GetColumnOffset(column_index+1) - GetColumnOffset(column_index);
+    return OffsetNormToPixels(window->DC.ColumnsData[column_index+1].OffsetNorm - window->DC.ColumnsData[column_index].OffsetNorm);
-    return w;
+}
+
+void ImGui::SetColumnWidth(int column_index, float width)
+{
+    ImGuiWindow* window = GetCurrentWindowRead();
+    if (column_index < 0)
+        column_index = window->DC.ColumnsCurrent;
+
+    SetColumnOffset(column_index+1, GetColumnOffset(column_index) + width);
 }
 
 static void PushColumnClipRect(int column_index)
@@ -9365,26 +9397,66 @@ static void PushColumnClipRect(int column_index)
     ImGui::PushClipRect(ImVec2(x1,-FLT_MAX), ImVec2(x2,+FLT_MAX), true);
 }
 
-void ImGui::Columns(int columns_count, const char* id, bool border)
+void ImGui::BeginColumns(const char* id, int columns_count, ImGuiColumnsFlags flags)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = GetCurrentWindow();
-    IM_ASSERT(columns_count >= 1);
+    IM_ASSERT(columns_count > 1);
+    IM_ASSERT(window->DC.ColumnsCount == 1); // Nested columns are currently not supported
 
-    if (window->DC.ColumnsCount != 1)
+    // Differentiate column ID with an arbitrary prefix for cases where users name their columns set the same as another widget.
+    // In addition, when an identifier isn't explicitly provided we include the number of columns in the hash to make it uniquer.
+    PushID(0x11223347 + (id ? 0 : columns_count));
+    window->DC.ColumnsSetId = window->GetID(id ? id : "columns");
+    PopID();
+
+    // Set state for first column
+    window->DC.ColumnsCurrent = 0;
+    window->DC.ColumnsCount = columns_count;
+    window->DC.ColumnsFlags = flags;
+
+    const float content_region_width = (window->SizeContentsExplicit.x != 0.0f) ? window->SizeContentsExplicit.x : window->Size.x;
+    window->DC.ColumnsMinX = window->DC.IndentX; // Lock our horizontal range
+    window->DC.ColumnsMaxX = content_region_width - window->Scroll.x - ((window->Flags & ImGuiWindowFlags_NoScrollbar) ? 0 : g.Style.ScrollbarSize);// - window->WindowPadding().x;
+    window->DC.ColumnsStartPosY = window->DC.CursorPos.y;
+    window->DC.ColumnsCellMinY = window->DC.ColumnsCellMaxY = window->DC.CursorPos.y;
+    window->DC.ColumnsOffsetX = 0.0f;
+    window->DC.CursorPos.x = (float)(int)(window->Pos.x + window->DC.IndentX + window->DC.ColumnsOffsetX);
+
+    // Cache column offsets
+    window->DC.ColumnsData.resize(columns_count + 1);
+    for (int column_index = 0; column_index < columns_count + 1; column_index++)
     {
+        const ImGuiID column_id = window->DC.ColumnsSetId + ImGuiID(column_index);
+        KeepAliveID(column_id);
+        const float default_t = column_index / (float)window->DC.ColumnsCount;
+        float t = window->DC.StateStorage->GetFloat(column_id, default_t);      // Cheaply store our floating point value inside the integer (could store a union into the map?)
+        if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoForceWithinWindow))
+            t = ImMin(t, PixelsToOffsetNorm(window->DC.ColumnsMaxX - g.Style.ColumnsMinSpacing * (window->DC.ColumnsCount - column_index)));
+        window->DC.ColumnsData[column_index].OffsetNorm = t;
+    }
+    window->DrawList->ChannelsSplit(window->DC.ColumnsCount);
+    PushColumnClipRect();
+    PushItemWidth(GetColumnWidth() * 0.65f);
+}
+
+void ImGui::EndColumns()
+{
+	ImGuiContext& g = *GImGui;
+	ImGuiWindow* window = GetCurrentWindow();
+	IM_ASSERT(window->DC.ColumnsCount > 1);
+
 	if (window->DC.ColumnsCurrent != 0)
-            ItemSize(ImVec2(0,0));   // Advance to column 0
+		ItemSize(ImVec2(0, 0));   // Advance to column 0
 	PopItemWidth();
 	PopClipRect();
 	window->DrawList->ChannelsMerge();
 
 	window->DC.ColumnsCellMaxY = ImMax(window->DC.ColumnsCellMaxY, window->DC.CursorPos.y);
 	window->DC.CursorPos.y = window->DC.ColumnsCellMaxY;
-    }
 
-    // Draw columns borders and handle resize at the time of "closing" a columns set
+	// Draw columns borders and handle resize
-    if (window->DC.ColumnsCount != columns_count && window->DC.ColumnsCount != 1 && window->DC.ColumnsShowBorders && !window->SkipItems)
+	if (!(window->DC.ColumnsFlags & ImGuiColumnsFlags_NoBorder) && !window->SkipItems)
 	{
 		const float y1 = window->DC.ColumnsStartPosY;
 		const float y2 = window->DC.CursorPos.y;
@@ -9392,7 +9464,7 @@ void ImGui::Columns(int columns_count, const char* id, bool border)
 		{
 			float x = window->Pos.x + GetColumnOffset(i);
 			const ImGuiID column_id = window->DC.ColumnsSetId + ImGuiID(i);
-            const ImRect column_rect(ImVec2(x-4,y1),ImVec2(x+4,y2));
+			const ImRect column_rect(ImVec2(x - 4, y1), ImVec2(x + 4, y2));
 			if (IsClippedEx(column_rect, &column_id, false))
 				continue;
 
@@ -9404,7 +9476,7 @@ void ImGui::Columns(int columns_count, const char* id, bool border)
 			// Draw before resize so our items positioning are in sync with the line being drawn
 			const ImU32 col = GetColorU32(held ? ImGuiCol_ColumnActive : hovered ? ImGuiCol_ColumnHovered : ImGuiCol_Column);
 			const float xi = (float)(int)x;
-            window->DrawList->AddLine(ImVec2(xi, y1+1.0f), ImVec2(xi, y2), col);
+			window->DrawList->AddLine(ImVec2(xi, y1 + 1.0f), ImVec2(xi, y2), col);
 
 			if (held)
 			{
@@ -9416,45 +9488,27 @@ void ImGui::Columns(int columns_count, const char* id, bool border)
 		}
 	}
 
-    // Differentiate column ID with an arbitrary prefix for cases where users name their columns set the same as another widget.
+	window->DC.ColumnsSetId = 0;
-    // In addition, when an identifier isn't explicitly provided we include the number of columns in the hash to make it uniquer.
-    PushID(0x11223347 + (id ? 0 : columns_count));
-    window->DC.ColumnsSetId = window->GetID(id ? id : "columns");
-    PopID();
-
-    // Set state for first column
 	window->DC.ColumnsCurrent = 0;
-    window->DC.ColumnsCount = columns_count;
+	window->DC.ColumnsCount = 1;
-    window->DC.ColumnsShowBorders = border;
+	window->DC.ColumnsFlags = 0;
-
-    const float content_region_width = (window->SizeContentsExplicit.x != 0.0f) ? window->SizeContentsExplicit.x : window->Size.x;
-    window->DC.ColumnsMinX = window->DC.IndentX; // Lock our horizontal range
-    window->DC.ColumnsMaxX = content_region_width - window->Scroll.x - ((window->Flags & ImGuiWindowFlags_NoScrollbar) ? 0 : g.Style.ScrollbarSize);// - window->WindowPadding().x;
-    window->DC.ColumnsStartPosY = window->DC.CursorPos.y;
-    window->DC.ColumnsCellMinY = window->DC.ColumnsCellMaxY = window->DC.CursorPos.y;
-    window->DC.ColumnsOffsetX = 0.0f;
-    window->DC.CursorPos.x = (float)(int)(window->Pos.x + window->DC.IndentX + window->DC.ColumnsOffsetX);
-
-    if (window->DC.ColumnsCount != 1)
-    {
-        // Cache column offsets
-        window->DC.ColumnsData.resize(columns_count + 1);
-        for (int column_index = 0; column_index < columns_count + 1; column_index++)
-        {
-            const ImGuiID column_id = window->DC.ColumnsSetId + ImGuiID(column_index);
-            KeepAliveID(column_id);
-            const float default_t = column_index / (float)window->DC.ColumnsCount;
-            const float t = window->DC.StateStorage->GetFloat(column_id, default_t);      // Cheaply store our floating point value inside the integer (could store a union into the map?)
-            window->DC.ColumnsData[column_index].OffsetNorm = t;
-        }
-        window->DrawList->ChannelsSplit(window->DC.ColumnsCount);
-        PushColumnClipRect();
-        PushItemWidth(GetColumnWidth() * 0.65f);
-    }
-    else
-    {
 	window->DC.ColumnsData.resize(0);
-    }
+}
+
+void ImGui::Columns(int columns_count, const char* id, bool border)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = GetCurrentWindow();
+    IM_ASSERT(columns_count >= 1);
+
+	ImGuiColumnsFlags flags = 0;
+	flags |= (border ? 0 : ImGuiColumnsFlags_NoBorder);
+
+	if (window->DC.ColumnsCount != columns_count && window->DC.ColumnsCount != 1)
+		EndColumns();
+
+    if (columns_count != 1)
+        BeginColumns(id, columns_count, flags);
 }
 
 void ImGui::Indent(float indent_w)

imgui.h

@@ -73,6 +73,7 @@ typedef int ImGuiKey;               // a key identifier (ImGui-side enum)   // e
 typedef int ImGuiColorEditMode;     // color edit mode for ColorEdit*()     // enum ImGuiColorEditMode_
 typedef int ImGuiMouseCursor;       // a mouse cursor identifier            // enum ImGuiMouseCursor_
 typedef int ImGuiWindowFlags;       // window flags for Begin*()            // enum ImGuiWindowFlags_
+typedef int ImGuiColumnsFlags;       // column flags for Columns()           // enum ImGuiColumnsFlags_
 typedef int ImGuiSetCond;           // condition flags for Set*()           // enum ImGuiSetCond_
 typedef int ImGuiInputTextFlags;    // flags for InputText*()               // enum ImGuiInputTextFlags_
 typedef int ImGuiSelectableFlags;   // flags for Selectable()               // enum ImGuiSelectableFlags_
@@ -221,13 +222,16 @@ namespace ImGui
 
     // Columns
     // You can also use SameLine(pos_x) for simplified columning. The columns API is still work-in-progress and rather lacking.
-    IMGUI_API void          Columns(int count = 1, const char* id = NULL, bool border = true);  // setup number of columns. use an identifier to distinguish multiple column sets. close with Columns(1).
+    IMGUI_API void          BeginColumns(const char* id, int count, ImGuiColumnsFlags flags = 0); // setup number of columns. use an identifier to distinguish multiple column sets. close with EndColumns().
-    IMGUI_API void          NextColumn();                                                       // next column
+    IMGUI_API void          EndColumns();                                                        // close columns
+    IMGUI_API void          NextColumn();                                                        // next column, defaults to current row or next row if the current row is finished
     IMGUI_API int           GetColumnIndex();                                                    // get current column index
-    IMGUI_API float         GetColumnOffset(int column_index = -1);                             // get position of column line (in pixels, from the left side of the contents region). pass -1 to use current column, otherwise 0..GetcolumnsCount() inclusive. column 0 is usually 0.0f and not resizable unless you call this
+    IMGUI_API float         GetColumnWidth(int column_index = -1);                               // get column width (in pixels). pass -1 to use current column
+    IMGUI_API void          SetColumnWidth(int column_index, float width);                       // set column width (in pixels). pass -1 to use current column
+    IMGUI_API float         GetColumnOffset(int column_index = -1);                              // get position of column line (in pixels, from the left side of the contents region). pass -1 to use current column, otherwise 0..GetColumnsCount() inclusive. column 0 is usually 0.0f and not resizable unless you call this
     IMGUI_API void          SetColumnOffset(int column_index, float offset_x);                   // set position of column line (in pixels, from the left side of the contents region). pass -1 to use current column
-    IMGUI_API float         GetColumnWidth(int column_index = -1);                              // column width (== GetColumnOffset(GetColumnIndex()+1) - GetColumnOffset(GetColumnOffset())
+    IMGUI_API int           GetColumnsCount();
-    IMGUI_API int           GetColumnsCount();                                                  // number of columns (what was passed to Columns())
+    IMGUI_API void          Columns(int count = 1, const char* id = NULL, bool border = true);
 
     // ID scopes
     // If you are creating widgets in a loop you most likely want to push a unique identifier so ImGui can differentiate them.
@@ -506,6 +510,15 @@ enum ImGuiWindowFlags_
     ImGuiWindowFlags_ChildMenu              = 1 << 27   // Don't use! For internal use by BeginMenu()
 };
 
+// Flags for ImGui::Columns()
+enum ImGuiColumnsFlags_
+{
+    // Default: 0
+    ImGuiColumnsFlags_NoBorder               = 1 << 0,   // Disable column dividers
+    ImGuiColumnsFlags_NoPreserveWidths       = 1 << 1,   // Disable column width preservation when adjusting columns
+    ImGuiColumnsFlags_NoForceWithinWindow    = 1 << 2    // Disable forcing columns to fit within window
+};
+
 // Flags for ImGui::InputText()
 enum ImGuiInputTextFlags_
 {

imgui_demo.cpp

@@ -1400,6 +1400,49 @@ void ImGui::ShowTestWindow(bool* p_open)
         }
         */
 
+        if (ImGui::TreeNode("Advanced settings"))
+        {
+            static bool border = true;
+            static bool preserveWidths = true;
+            static bool forceWithinWindow = true;
+
+            ImGui::Checkbox("Border", &border);
+            ImGui::SameLine();
+            ImGui::Checkbox("Preserve widths", &preserveWidths);
+            ImGui::SameLine();
+            ImGui::Checkbox("Force within window", &forceWithinWindow);
+
+            ImGuiColumnsFlags flags = 0;
+            flags |= (border ? 0 : ImGuiColumnsFlags_NoBorder);
+            flags |= (preserveWidths ? 0 : ImGuiColumnsFlags_NoPreserveWidths);
+            flags |= (forceWithinWindow ? 0 : ImGuiColumnsFlags_NoForceWithinWindow);
+
+            ImGui::BeginColumns("AdvancedColumns", 4, flags);
+            ImGui::Separator();
+            ImGui::Text("ID"); ImGui::NextColumn();
+            ImGui::Text("Name"); ImGui::NextColumn();
+            ImGui::Text("Path"); ImGui::NextColumn();
+            ImGui::Text("Flags"); ImGui::NextColumn();
+            ImGui::Separator();
+            const char* names[3] = { "One", "Two", "Three" };
+            const char* paths[3] = { "/path/one", "/path/two", "/path/three" };
+            static int selected = -1;
+            for (int i = 0; i < 3; i++)
+            {
+                char label[32];
+                sprintf(label, "%04d", i);
+                if (ImGui::Selectable(label, selected == i, ImGuiSelectableFlags_SpanAllColumns))
+                    selected = i;
+                ImGui::NextColumn();
+                ImGui::Text(names[i]); ImGui::NextColumn();
+                ImGui::Text(paths[i]); ImGui::NextColumn();
+                ImGui::Text("...."); ImGui::NextColumn();
+            }
+            ImGui::EndColumns();
+            ImGui::Separator();
+            ImGui::TreePop();
+        }
+
         // Create multiple items in a same cell before switching to next column
         if (ImGui::TreeNode("Mixed items"))
         {

imgui_internal.h

@@ -571,7 +571,7 @@ struct IMGUI_API ImGuiDrawContext
     float                   ColumnsStartPosY;
     float                   ColumnsCellMinY;
     float                   ColumnsCellMaxY;
-    bool                    ColumnsShowBorders;
+    ImGuiColumnsFlags        ColumnsFlags;
     ImGuiID                 ColumnsSetId;
     ImVector<ImGuiColumnData> ColumnsData;
 
@@ -603,7 +603,7 @@ struct IMGUI_API ImGuiDrawContext
         ColumnsMinX = ColumnsMaxX = 0.0f;
         ColumnsStartPosY = 0.0f;
         ColumnsCellMinY = ColumnsCellMaxY = 0.0f;
-        ColumnsShowBorders = true;
+        ColumnsFlags = 0;
         ColumnsSetId = 0;
     }
 };