Tabs: added new fitting policy ImGuiTabBarFlags_FittingPolicyMixed, new default. (#3421, #8800)

docs/CHANGELOG.txt

@@ -54,11 +54,17 @@ Other Changes:
   often more convenient to use index in caller-code, whereas TableGetRowIndex()
   includes header rows). 
 - Tables: fixed imgui_internal.h's TableGetHoveredRow() the same way. (#7350, #6588, #6250)
-- Tabs: fixed tab bar underline not drawing below scroll buttons, when
-  they are enabled (minor regression from 1.90). (#6820, #4859, #5022, #5239)
+- Tabs: added new fitting policy ImGuiTabBarFlags_FittingPolicyMixed
+  and made it the default. This policy shrink tab width down to a given amount,
+  and then beyond that it enable scrolling buttons. (#3421, #8800)
+- Tabs: added style.TabMinWidthShrink, ImGuiStyleVar_TabMinWidthShrink to
+  control the width to shrink to in ImGuiTabBarFlags_FittingPolicyMixed mode.
+  (#3421, #8800). 
 - Tabs: added style.TabMinWidthBase, ImGuiStyleVar_TabMinWidthBase to control
   the base minimum width of a tab (default to 1.0f). This is the size before
   any potential shrinking is applied.
+- Tabs: fixed tab bar underline not drawing below scroll buttons, when
+  they are enabled (minor regression from 1.90). (#6820, #4859, #5022, #5239)
 - Error Handling: minor improvements to error handling for TableGetSortSpecs()
   and TableSetBgColor() calls. (#1651, #8499)
 - Misc: fixed building with IMGUI_DISABLE_DEBUG_TOOLS only. (#8796)

imgui.cpp

@@ -1419,6 +1419,7 @@ ImGuiStyle::ImGuiStyle()
     TabRounding                 = 5.0f;             // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
     TabBorderSize               = 0.0f;             // Thickness of border around tabs.
     TabMinWidthBase             = 1.0f;             // Minimum tab width, to make tabs larger than their contents. TabBar buttons are not affected.
+    TabMinWidthShrink           = 80.0f;            // Minimum tab width after shrinking, when using ImGuiTabBarFlags_FittingPolicyMixed policy.
     TabCloseButtonMinWidthSelected   = -1.0f;       // -1: always visible. 0.0f: visible when hovered. >0.0f: visible when hovered if minimum width.
     TabCloseButtonMinWidthUnselected = 0.0f;        // -1: always visible. 0.0f: visible when hovered. >0.0f: visible when hovered if minimum width. FLT_MAX: never show close button when unselected.
     TabBarBorderSize            = 1.0f;             // Thickness of tab-bar separator, which takes on the tab active color to denote focus.
@@ -1486,6 +1487,7 @@ void ImGuiStyle::ScaleAllSizes(float scale_factor)
     ImageBorderSize = ImTrunc(ImageBorderSize * scale_factor);
     TabRounding = ImTrunc(TabRounding * scale_factor);
     TabMinWidthBase = ImTrunc(TabMinWidthBase * scale_factor);
+    TabMinWidthShrink = ImTrunc(TabMinWidthShrink * scale_factor);
     TabCloseButtonMinWidthSelected = (TabCloseButtonMinWidthSelected > 0.0f && TabCloseButtonMinWidthSelected != FLT_MAX) ? ImTrunc(TabCloseButtonMinWidthSelected * scale_factor) : TabCloseButtonMinWidthSelected;
     TabCloseButtonMinWidthUnselected = (TabCloseButtonMinWidthUnselected > 0.0f && TabCloseButtonMinWidthUnselected != FLT_MAX) ? ImTrunc(TabCloseButtonMinWidthUnselected * scale_factor) : TabCloseButtonMinWidthUnselected;
     TabBarOverlineSize = ImTrunc(TabBarOverlineSize * scale_factor);
@@ -3506,6 +3508,7 @@ static const ImGuiStyleVarInfo GStyleVarsInfo[] =
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabRounding) },               // ImGuiStyleVar_TabRounding
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabBorderSize) },             // ImGuiStyleVar_TabBorderSize
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabMinWidthBase) },           // ImGuiStyleVar_TabMinWidthBase
+    { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabMinWidthShrink) },         // ImGuiStyleVar_TabMinWidthShrink
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabBarBorderSize) },          // ImGuiStyleVar_TabBarBorderSize
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TabBarOverlineSize) },        // ImGuiStyleVar_TabBarOverlineSize
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TableAngledHeadersAngle)},    // ImGuiStyleVar_TableAngledHeadersAngle

imgui.h

@@ -1372,10 +1372,11 @@ enum ImGuiTabBarFlags_
     ImGuiTabBarFlags_DrawSelectedOverline           = 1 << 6,   // Draw selected overline markers over selected tab
 
     // Fitting/Resize policy
-    ImGuiTabBarFlags_FittingPolicyShrink            = 1 << 7,   // Shrink down tabs when they don't fit
-    ImGuiTabBarFlags_FittingPolicyScroll            = 1 << 8,   // Add scroll buttons when tabs don't fit
-    ImGuiTabBarFlags_FittingPolicyMask_             = ImGuiTabBarFlags_FittingPolicyShrink | ImGuiTabBarFlags_FittingPolicyScroll,
-    ImGuiTabBarFlags_FittingPolicyDefault_          = ImGuiTabBarFlags_FittingPolicyShrink,
+    ImGuiTabBarFlags_FittingPolicyMixed             = 1 << 7,   // Shrink down tabs when they don't fit, until width is style.TabMinWidthShrink, then enable scrolling buttons.
+    ImGuiTabBarFlags_FittingPolicyShrink            = 1 << 8,   // Shrink down tabs when they don't fit
+    ImGuiTabBarFlags_FittingPolicyScroll            = 1 << 9,   // Enable scrolling buttons when tabs don't fit
+    ImGuiTabBarFlags_FittingPolicyMask_             = ImGuiTabBarFlags_FittingPolicyMixed | ImGuiTabBarFlags_FittingPolicyShrink | ImGuiTabBarFlags_FittingPolicyScroll,
+    ImGuiTabBarFlags_FittingPolicyDefault_          = ImGuiTabBarFlags_FittingPolicyMixed,
 
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     ImGuiTabBarFlags_FittingPolicyResizeDown        = ImGuiTabBarFlags_FittingPolicyShrink, // Renamed in 1.92.2
@@ -1810,6 +1811,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_TabRounding,              // float     TabRounding
     ImGuiStyleVar_TabBorderSize,            // float     TabBorderSize
     ImGuiStyleVar_TabMinWidthBase,          // float     TabMinWidthBase
+    ImGuiStyleVar_TabMinWidthShrink,        // float     TabMinWidthShrink
     ImGuiStyleVar_TabBarBorderSize,         // float     TabBarBorderSize
     ImGuiStyleVar_TabBarOverlineSize,       // float     TabBarOverlineSize
     ImGuiStyleVar_TableAngledHeadersAngle,  // float     TableAngledHeadersAngle
@@ -2276,6 +2278,7 @@ struct ImGuiStyle
     float       TabRounding;                // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
     float       TabBorderSize;              // Thickness of border around tabs.
     float       TabMinWidthBase;            // Minimum tab width, to make tabs larger than their contents. TabBar buttons are not affected.
+    float       TabMinWidthShrink;          // Minimum tab width after shrinking, when using ImGuiTabBarFlags_FittingPolicyMixed policy.
     float       TabCloseButtonMinWidthSelected;     // -1: always visible. 0.0f: visible when hovered. >0.0f: visible when hovered if minimum width.
     float       TabCloseButtonMinWidthUnselected;   // -1: always visible. 0.0f: visible when hovered. >0.0f: visible when hovered if minimum width. FLT_MAX: never show close button when unselected.
     float       TabBarBorderSize;           // Thickness of tab-bar separator, which takes on the tab active color to denote focus.

imgui_demo.cpp

@@ -3383,6 +3383,8 @@ static void EditTabBarFittingPolicyFlags(ImGuiTabBarFlags* p_flags)
 {
     if ((*p_flags & ImGuiTabBarFlags_FittingPolicyMask_) == 0)
         *p_flags |= ImGuiTabBarFlags_FittingPolicyDefault_;
+    if (ImGui::CheckboxFlags("ImGuiTabBarFlags_FittingPolicyMixed", p_flags, ImGuiTabBarFlags_FittingPolicyMixed))
+        *p_flags &= ~(ImGuiTabBarFlags_FittingPolicyMask_ ^ ImGuiTabBarFlags_FittingPolicyMixed);
     if (ImGui::CheckboxFlags("ImGuiTabBarFlags_FittingPolicyShrink", p_flags, ImGuiTabBarFlags_FittingPolicyShrink))
         *p_flags &= ~(ImGuiTabBarFlags_FittingPolicyMask_ ^ ImGuiTabBarFlags_FittingPolicyShrink);
     if (ImGui::CheckboxFlags("ImGuiTabBarFlags_FittingPolicyScroll", p_flags, ImGuiTabBarFlags_FittingPolicyScroll))
@@ -8343,6 +8345,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             SliderFloat("TabBarOverlineSize", &style.TabBarOverlineSize, 0.0f, 3.0f, "%.0f");
             SameLine(); HelpMarker("Overline is only drawn over the selected tab when ImGuiTabBarFlags_DrawSelectedOverline is set.");
             DragFloat("TabMinWidthBase", &style.TabMinWidthBase, 0.5f, 1.0f, 500.0f, "%.0f");
+            DragFloat("TabMinWidthShrink", &style.TabMinWidthShrink, 0.5f, 1.0f, 500.0f, "%0.f");
             DragFloat("TabCloseButtonMinWidthSelected", &style.TabCloseButtonMinWidthSelected, 0.5f, -1.0f, 100.0f, (style.TabCloseButtonMinWidthSelected < 0.0f) ? "%.0f (Always)" : "%.0f");
             DragFloat("TabCloseButtonMinWidthUnselected", &style.TabCloseButtonMinWidthUnselected, 0.5f, -1.0f, 100.0f, (style.TabCloseButtonMinWidthUnselected < 0.0f) ? "%.0f (Always)" : "%.0f");
             SliderFloat("TabRounding", &style.TabRounding, 0.0f, 12.0f, "%.0f");

imgui_internal.h

@@ -2776,6 +2776,7 @@ struct IMGUI_API ImGuiTabBar
     bool                WantLayout;
     bool                VisibleTabWasSubmitted;
     bool                TabsAddedNew;           // Set to true when a new tab item or button has been added to the tab bar during last frame
+    bool                ScrollButtonEnabled;
     ImS16               TabsActiveCount;        // Number of tabs submitted this frame.
     ImS16               LastTabItemIdx;         // Index of last BeginTabItem() tab for use by EndTabItem()
     float               ItemSpacingY;
@@ -3222,7 +3223,7 @@ namespace ImGui
     IMGUI_API ImVec2        CalcItemSize(ImVec2 size, float default_w, float default_h);
     IMGUI_API float         CalcWrapWidthForPos(const ImVec2& pos, float wrap_pos_x);
     IMGUI_API void          PushMultiItemsWidths(int components, float width_full);
-    IMGUI_API void          ShrinkWidths(ImGuiShrinkWidthItem* items, int count, float width_excess);
+    IMGUI_API void          ShrinkWidths(ImGuiShrinkWidthItem* items, int count, float width_excess, float width_min);
 
     // Parameter stacks (shared)
     IMGUI_API const ImGuiStyleVarInfo* GetStyleVarInfo(ImGuiStyleVar idx);

imgui_widgets.cpp

@@ -1830,27 +1830,31 @@ static int IMGUI_CDECL ShrinkWidthItemComparer(const void* lhs, const void* rhs)
 
 // Shrink excess width from a set of item, by removing width from the larger items first.
 // Set items Width to -1.0f to disable shrinking this item.
-void ImGui::ShrinkWidths(ImGuiShrinkWidthItem* items, int count, float width_excess)
+void ImGui::ShrinkWidths(ImGuiShrinkWidthItem* items, int count, float width_excess, float width_min)
 {
     if (count == 1)
     {
         if (items[0].Width >= 0.0f)
-            items[0].Width = ImMax(items[0].Width - width_excess, 1.0f);
+            items[0].Width = ImMax(items[0].Width - width_excess, width_min);
         return;
     }
-    ImQsort(items, (size_t)count, sizeof(ImGuiShrinkWidthItem), ShrinkWidthItemComparer);
+    ImQsort(items, (size_t)count, sizeof(ImGuiShrinkWidthItem), ShrinkWidthItemComparer); // Sort largest first, smallest last.
     int count_same_width = 1;
     while (width_excess > 0.0f && count_same_width < count)
     {
         while (count_same_width < count && items[0].Width <= items[count_same_width].Width)
             count_same_width++;
         float max_width_to_remove_per_item = (count_same_width < count && items[count_same_width].Width >= 0.0f) ? (items[0].Width - items[count_same_width].Width) : (items[0].Width - 1.0f);
+        max_width_to_remove_per_item = ImMin(items[0].Width - width_min, max_width_to_remove_per_item);
         if (max_width_to_remove_per_item <= 0.0f)
             break;
-        float width_to_remove_per_item = ImMin(width_excess / count_same_width, max_width_to_remove_per_item);
+        float base_width_to_remove_per_item = ImMin(width_excess / count_same_width, max_width_to_remove_per_item);
         for (int item_n = 0; item_n < count_same_width; item_n++)
-            items[item_n].Width -= width_to_remove_per_item;
-        width_excess -= width_to_remove_per_item * count_same_width;
+        {
+            float width_to_remove_for_this_item = ImMin(base_width_to_remove_per_item, items[item_n].Width - width_min);
+            items[item_n].Width -= width_to_remove_for_this_item;
+            width_excess -= width_to_remove_for_this_item;
+        }
     }
 
     // Round width and redistribute remainder
@@ -9358,6 +9362,7 @@ struct ImGuiTabBarSection
 {
     int                 TabCount;               // Number of tabs in this section.
     float               Width;                  // Sum of width of tabs in this section (after shrinking down)
+    float               WidthAfterShrinkMinWidth;
     float               Spacing;                // Horizontal spacing at the end of the section.
 
     ImGuiTabBarSection() { memset(this, 0, sizeof(*this)); }
@@ -9626,6 +9631,9 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     int shrink_buffer_indexes[3] = { 0, sections[0].TabCount + sections[2].TabCount, sections[0].TabCount };
     g.ShrinkWidthBuffer.resize(tab_bar->Tabs.Size);
 
+    // Minimum shrink width
+    const float shrink_min_width = (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyMixed) ? g.Style.TabMinWidthShrink : 1.0f;
+
     // Compute ideal tabs widths + store them into shrink buffer
     ImGuiTabItem* most_recently_selected_tab = NULL;
     int curr_section_n = -1;
@@ -9654,6 +9662,7 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
         int section_n = TabItemGetSectionIdx(tab);
         ImGuiTabBarSection* section = &sections[section_n];
         section->Width += tab->ContentWidth + (section_n == curr_section_n ? g.Style.ItemInnerSpacing.x : 0.0f);
+        section->WidthAfterShrinkMinWidth += ImMin(tab->ContentWidth, shrink_min_width) + (section_n == curr_section_n ? g.Style.ItemInnerSpacing.x : 0.0f);
         curr_section_n = section_n;
 
         // Store data so we can build an array sorted by width if we need to shrink tabs down
@@ -9665,13 +9674,19 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     }
 
     // Compute total ideal width (used for e.g. auto-resizing a window)
+    float width_all_tabs_after_min_width_shrink = 0.0f;
     tab_bar->WidthAllTabsIdeal = 0.0f;
     for (int section_n = 0; section_n < 3; section_n++)
+    {
         tab_bar->WidthAllTabsIdeal += sections[section_n].Width + sections[section_n].Spacing;
+        width_all_tabs_after_min_width_shrink += sections[section_n].WidthAfterShrinkMinWidth + sections[section_n].Spacing;
+    }
 
     // Horizontal scrolling buttons
     // Important: note that TabBarScrollButtons() will alter BarRect.Max.x.
-    if ((tab_bar->WidthAllTabsIdeal > tab_bar->BarRect.GetWidth() && tab_bar->Tabs.Size > 1) && !(tab_bar->Flags & ImGuiTabBarFlags_NoTabListScrollingButtons) && (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyScroll))
+    const bool can_scroll = (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyScroll) || (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyMixed);
+    tab_bar->ScrollButtonEnabled = ((width_all_tabs_after_min_width_shrink > tab_bar->BarRect.GetWidth() && tab_bar->Tabs.Size > 1) && !(tab_bar->Flags & ImGuiTabBarFlags_NoTabListScrollingButtons) && can_scroll);
+    if (tab_bar->ScrollButtonEnabled)
         if (ImGuiTabItem* scroll_and_select_tab = TabBarScrollingButtons(tab_bar))
         {
             scroll_to_tab_id = scroll_and_select_tab->ID;
@@ -9691,11 +9706,12 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
         width_excess = (section_0_w + section_2_w) - tab_bar->BarRect.GetWidth(); // Excess used to shrink leading/trailing section
 
     // With ImGuiTabBarFlags_FittingPolicyScroll policy, we will only shrink leading/trailing if the central section is not visible anymore
-    if (width_excess >= 1.0f && ((tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyShrink) || !central_section_is_visible))
+    const bool can_shrink = (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyShrink) || (tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyMixed);
+    if (width_excess >= 1.0f && (can_shrink || !central_section_is_visible))
     {
         int shrink_data_count = (central_section_is_visible ? sections[1].TabCount : sections[0].TabCount + sections[2].TabCount);
         int shrink_data_offset = (central_section_is_visible ? sections[0].TabCount + sections[2].TabCount : 0);
-        ShrinkWidths(g.ShrinkWidthBuffer.Data + shrink_data_offset, shrink_data_count, width_excess);
+        ShrinkWidths(g.ShrinkWidthBuffer.Data + shrink_data_offset, shrink_data_count, width_excess, shrink_min_width);
 
         // Apply shrunk values into tabs and sections
         for (int tab_n = shrink_data_offset; tab_n < shrink_data_offset + shrink_data_count; tab_n++)
@@ -9750,7 +9766,7 @@ static void ImGui::TabBarLayout(ImGuiTabBar* tab_bar)
     // Apply request requests
     if (scroll_to_tab_id != 0)
         TabBarScrollToTab(tab_bar, scroll_to_tab_id, sections);
-    else if ((tab_bar->Flags & ImGuiTabBarFlags_FittingPolicyScroll) && IsMouseHoveringRect(tab_bar->BarRect.Min, tab_bar->BarRect.Max, true) && IsWindowContentHoverable(g.CurrentWindow))
+    else if (tab_bar->ScrollButtonEnabled && IsMouseHoveringRect(tab_bar->BarRect.Min, tab_bar->BarRect.Max, true) && IsWindowContentHoverable(g.CurrentWindow))
     {
         const float wheel = g.IO.MouseWheelRequestAxisSwap ? g.IO.MouseWheel : g.IO.MouseWheelH;
         const ImGuiKey wheel_key = g.IO.MouseWheelRequestAxisSwap ? ImGuiKey_MouseWheelY : ImGuiKey_MouseWheelX;