Added BETA api for Tab Bar/Tabs widgets. (ocornut#261, ocornut#351) (merged this feature from the from Docking branch so it can be used earlier as as standalone feature)

- Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
- Added ImGuiTabBarFlags flags for BeginTabBar().
- Added ImGuiTabItemFlags flags for BeginTabItem().
- Style: Added ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive colors.
- Demo: Added Layout->Tabs demo code.
- Demo: Added "Documents" example app showcasing possible use for tabs.

Author: ocornut

docs/CHANGELOG.txt

@@ -39,6 +39,15 @@ Breaking Changes:
   The addition of new configuration options in the Docking branch is pushing for a little reorganization of those names.
 
 Other Changes:
+- Added BETA api for Tab Bar/Tabs widgets: (#261, #351)
+  - Added BeginTabBar(), EndTabBar(), BeginTabItem(), EndTabItem(), SetTabItemClosed() API.
+  - Added ImGuiTabBarFlags flags for BeginTabBar().
+  - Added ImGuiTabItemFlags flags for BeginTabItem().
+  - Style: Added ImGuiCol_Tab, ImGuiCol_TabHovered, ImGuiCol_TabActive, ImGuiCol_TabUnfocused, ImGuiCol_TabUnfocusedActive colors.
+  - Demo: Added Layout->Tabs demo code.
+  - Demo: Added "Documents" example app showcasing possible use for tabs.
+  This feature was merged from the Docking branch in order to allow the use of regular tabs in your code.
+  (It does not provide the docking/splitting/merging of windows available in the Docking branch)
 - Added ImGuiWindowFlags_UnsavedDocument window flag to append '*' to title without altering 
   the ID, as a convenience to avoid using the ### operator.
 - Resizing windows from edge is now enabled by default (io.ConfigWindowsResizeFromEdges=true). Note that 

docs/TODO.txt

@@ -127,7 +127,8 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - dock: docking extension
  - dock: dock out from a collapsing header? would work nicely but need emitting window to keep submitting the code.
 
- - tabs: re-ordering, close buttons, context menu, persistent order (#261, #351)
+ - tabs: make EndTabBar fail if users doesn't respect BeginTabBar return value, for consistency/future-proofing.
+ - tabs: persistent order/focus in BeginTabBar() api (#261, #351)
 
  - ext: stl-ish friendly extension (imgui_stl.h) that has wrapper for std::string, std::vector etc.
 

imgui.cpp

@@ -1015,6 +1015,8 @@ ImGuiStyle::ImGuiStyle()
     ScrollbarRounding       = 9.0f;             // Radius of grab corners rounding for scrollbar
     GrabMinSize             = 10.0f;            // Minimum width/height of a grab box for slider/scrollbar
     GrabRounding            = 0.0f;             // Radius of grabs corners rounding. Set to 0.0f to have rectangular slider grabs.
+    TabRounding             = 4.0f;             // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
+    TabBorderSize           = 0.0f;             // Thickness of border around tabs.
     ButtonTextAlign         = ImVec2(0.5f,0.5f);// Alignment of button text when button is larger than text.
     DisplayWindowPadding    = ImVec2(19,19);    // Window position are clamped to be visible within the display area by at least this amount. Only applies to regular windows.
     DisplaySafeAreaPadding  = ImVec2(3,3);      // If you cannot see the edge of your screen (e.g. on a TV) increase the safe area padding. Covers popups/tooltips as well regular windows.
@@ -1038,6 +1040,7 @@ void ImGuiStyle::ScaleAllSizes(float scale_factor)
     PopupRounding = ImFloor(PopupRounding * scale_factor);
     FramePadding = ImFloor(FramePadding * scale_factor);
     FrameRounding = ImFloor(FrameRounding * scale_factor);
+    TabRounding = ImFloor(TabRounding * scale_factor);
     ItemSpacing = ImFloor(ItemSpacing * scale_factor);
     ItemInnerSpacing = ImFloor(ItemInnerSpacing * scale_factor);
     TouchExtraPadding = ImFloor(TouchExtraPadding * scale_factor);
@@ -2160,17 +2163,8 @@ void ImGui::RenderTextWrapped(ImVec2 pos, const char* text, const char* text_end
 
 // Default clip_rect uses (pos_min,pos_max)
 // Handle clipping on CPU immediately (vs typically let the GPU clip the triangles that are overlapping the clipping rectangle edges)
-void ImGui::RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, const ImVec2& align, const ImRect* clip_rect)
+void ImGui::RenderTextClippedEx(ImDrawList* draw_list, const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_display_end, const ImVec2* text_size_if_known, const ImVec2& align, const ImRect* clip_rect)
 {
-    // Hide anything after a '##' string
-    const char* text_display_end = FindRenderedTextEnd(text, text_end);
-    const int text_len = (int)(text_display_end - text);
-    if (text_len == 0)
-        return;
-
-    ImGuiContext& g = *GImGui;
-    ImGuiWindow* window = g.CurrentWindow;
-
     // Perform CPU side clipping for single clipped element to avoid using scissor state
     ImVec2 pos = pos_min;
     const ImVec2 text_size = text_size_if_known ? *text_size_if_known : CalcTextSize(text, text_display_end, false, 0.0f);
@@ -2189,14 +2183,27 @@ void ImGui::RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, cons
     if (need_clipping)
     {
         ImVec4 fine_clip_rect(clip_min->x, clip_min->y, clip_max->x, clip_max->y);
-        window->DrawList->AddText(g.Font, g.FontSize, pos, GetColorU32(ImGuiCol_Text), text, text_display_end, 0.0f, &fine_clip_rect);
+        draw_list->AddText(NULL, 0.0f, pos, GetColorU32(ImGuiCol_Text), text, text_display_end, 0.0f, &fine_clip_rect);
     }
     else
     {
-        window->DrawList->AddText(g.Font, g.FontSize, pos, GetColorU32(ImGuiCol_Text), text, text_display_end, 0.0f, NULL);
+        draw_list->AddText(NULL, 0.0f, pos, GetColorU32(ImGuiCol_Text), text, text_display_end, 0.0f, NULL);
     }
+}
+
+void ImGui::RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, const ImVec2& align, const ImRect* clip_rect)
+{
+    // Hide anything after a '##' string
+    const char* text_display_end = FindRenderedTextEnd(text, text_end);
+    const int text_len = (int)(text_display_end - text);
+    if (text_len == 0)
+        return;
+
+    ImGuiContext& g = *GImGui;
+    ImGuiWindow* window = g.CurrentWindow;
+    RenderTextClippedEx(window->DrawList, pos_min, pos_max, text, text_display_end, text_size_if_known, align, clip_rect);
     if (g.LogEnabled)
-        LogRenderedText(&pos, text, text_display_end);
+        LogRenderedText(&pos_min, text, text_display_end);
 }
 
 // Render a rectangle shaped with optional rounding and borders
@@ -5511,6 +5518,7 @@ static const ImGuiStyleVarInfo GStyleVarInfo[] =
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, ScrollbarRounding) },  // ImGuiStyleVar_ScrollbarRounding
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, GrabMinSize) },        // ImGuiStyleVar_GrabMinSize
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, GrabRounding) },       // ImGuiStyleVar_GrabRounding
+    { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, TabRounding) },        // ImGuiStyleVar_TabRounding
     { ImGuiDataType_Float, 2, (ImU32)IM_OFFSETOF(ImGuiStyle, ButtonTextAlign) },    // ImGuiStyleVar_ButtonTextAlign
 };
 
@@ -5603,6 +5611,11 @@ const char* ImGui::GetStyleColorName(ImGuiCol idx)
     case ImGuiCol_ResizeGrip: return "ResizeGrip";
     case ImGuiCol_ResizeGripHovered: return "ResizeGripHovered";
     case ImGuiCol_ResizeGripActive: return "ResizeGripActive";
+    case ImGuiCol_Tab: return "Tab";
+    case ImGuiCol_TabHovered: return "TabHovered";
+    case ImGuiCol_TabActive: return "TabActive";
+    case ImGuiCol_TabUnfocused: return "TabUnfocused";
+    case ImGuiCol_TabUnfocusedActive: return "TabUnfocusedActive";
     case ImGuiCol_PlotLines: return "PlotLines";
     case ImGuiCol_PlotLinesHovered: return "PlotLinesHovered";
     case ImGuiCol_PlotHistogram: return "PlotHistogram";
@@ -9056,6 +9069,29 @@ void ImGui::ShowMetricsWindow(bool* p_open)
             ImGui::BulletText("Storage: %d bytes", window->StateStorage.Data.Size * (int)sizeof(ImGuiStorage::Pair));
             ImGui::TreePop();
         }
+
+        static void NodeTabBar(ImGuiTabBar* tab_bar)
+        {
+            // Standalone tab bars (not associated to docking/windows functionality) currently hold no discernable strings.
+            char buf[256];
+            char* p = buf;
+            const char* buf_end = buf + IM_ARRAYSIZE(buf);
+            p += ImFormatString(p, buf_end - p, "TabBar (%d tabs)%s",
+                tab_bar->Tabs.Size, (tab_bar->PrevFrameVisible < ImGui::GetFrameCount() - 2) ? " *Inactive*" : "");
+            if (ImGui::TreeNode(tab_bar, "%s", buf))
+            {
+                for (int tab_n = 0; tab_n < tab_bar->Tabs.Size; tab_n++)
+                {
+                    const ImGuiTabItem* tab = &tab_bar->Tabs[tab_n];
+                    ImGui::PushID(tab);
+                    if (ImGui::SmallButton("<")) { TabBarQueueChangeTabOrder(tab_bar, tab, -1); } ImGui::SameLine(0, 2);
+                    if (ImGui::SmallButton(">")) { TabBarQueueChangeTabOrder(tab_bar, tab, +1); } ImGui::SameLine();
+                    ImGui::Text("%02d%c Tab 0x%08X", tab_n, (tab->ID == tab_bar->SelectedTabId) ? '*' : ' ', tab->ID);
+                    ImGui::PopID();
+                }
+                ImGui::TreePop();
+            }
+        }
     };
 
     // Access private state, we are going to display the draw lists from last frame
@@ -9076,6 +9112,12 @@ void ImGui::ShowMetricsWindow(bool* p_open)
         }
         ImGui::TreePop();
     }
+    if (ImGui::TreeNode("TabBars", "Tab Bars (%d)", g.TabBars.Data.Size))
+    {
+        for (int n = 0; n < g.TabBars.Data.Size; n++)
+            Funcs::NodeTabBar(g.TabBars.GetByIndex(n));
+        ImGui::TreePop();
+    }
     if (ImGui::TreeNode("Internal state"))
     {
         const char* input_source_names[] = { "None", "Mouse", "Nav", "NavKeyboard", "NavGamepad" }; IM_ASSERT(IM_ARRAYSIZE(input_source_names) == ImGuiInputSource_COUNT);

imgui.h

@@ -135,6 +135,8 @@ typedef int ImGuiFocusedFlags;      // -> enum ImGuiFocusedFlags_    // Flags: f
 typedef int ImGuiHoveredFlags;      // -> enum ImGuiHoveredFlags_    // Flags: for IsItemHovered(), IsWindowHovered() etc.
 typedef int ImGuiInputTextFlags;    // -> enum ImGuiInputTextFlags_  // Flags: for InputText*()
 typedef int ImGuiSelectableFlags;   // -> enum ImGuiSelectableFlags_ // Flags: for Selectable()
+typedef int ImGuiTabBarFlags;       // -> enum ImGuiTabBarFlags_     // Flags: for BeginTabBar()
+typedef int ImGuiTabItemFlags;      // -> enum ImGuiTabItemFlags_    // Flags: for BeginTabItem()
 typedef int ImGuiTreeNodeFlags;     // -> enum ImGuiTreeNodeFlags_   // Flags: for TreeNode*(),CollapsingHeader()
 typedef int ImGuiWindowFlags;       // -> enum ImGuiWindowFlags_     // Flags: for Begin*()
 typedef int (*ImGuiInputTextCallback)(ImGuiInputTextCallbackData *data);
@@ -528,6 +530,14 @@ namespace ImGui
     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 int           GetColumnsCount();
 
+    // Tab Bars, Tabs
+    // [BETA API] API may evolve!
+    IMGUI_API bool          BeginTabBar(const char* str_id, ImGuiTabBarFlags flags = 0);        // create and append into a TabBar
+    IMGUI_API void          EndTabBar();
+    IMGUI_API bool          BeginTabItem(const char* label, bool* p_open = NULL, ImGuiTabItemFlags flags = 0);// create a Tab. Returns true if the Tab is selected.
+    IMGUI_API void          EndTabItem();                                                       // only call EndTabItem() if BeginTabItem() returns true!
+    IMGUI_API void          SetTabItemClosed(const char* tab_or_docked_window_label);           // notify TabBar or Docking system of a closed tab/window ahead (useful to reduce visual flicker on reorderable tab bars). For tab-bar: call after BeginTabBar() and before Tab submissions. Otherwise call with a window name.
+
     // Logging/Capture: all text output from interface is captured to tty/file/clipboard. By default, tree nodes are automatically opened during logging.
     IMGUI_API void          LogToTTY(int max_depth = -1);                                       // start logging to tty
     IMGUI_API void          LogToFile(int max_depth = -1, const char* filename = NULL);         // start logging to file
@@ -760,6 +770,31 @@ enum ImGuiComboFlags_
     ImGuiComboFlags_HeightMask_             = ImGuiComboFlags_HeightSmall | ImGuiComboFlags_HeightRegular | ImGuiComboFlags_HeightLarge | ImGuiComboFlags_HeightLargest
 };
 
+// Flags for ImGui::BeginTabBar()
+enum ImGuiTabBarFlags_
+{
+    ImGuiTabBarFlags_None                           = 0,
+    ImGuiTabBarFlags_Reorderable                    = 1 << 0,   // Allow manually dragging tabs to re-order them + New tabs are appended at the end of list
+    ImGuiTabBarFlags_AutoSelectNewTabs              = 1 << 1,   // Automatically select new tabs when they appear
+    ImGuiTabBarFlags_NoCloseWithMiddleMouseButton   = 1 << 2,   // Disable behavior of closing tabs (that are submitted with p_open != NULL) with middle mouse button. You can still repro this behavior on user's side with if (IsItemHovered() && IsMouseClicked(2)) *p_open = false.
+    ImGuiTabBarFlags_NoTabListPopupButton           = 1 << 3,
+    ImGuiTabBarFlags_NoTabListScrollingButtons      = 1 << 4,
+    ImGuiTabBarFlags_FittingPolicyResizeDown        = 1 << 5,   // Resize tabs when they don't fit
+    ImGuiTabBarFlags_FittingPolicyScroll            = 1 << 6,   // Add scroll buttons when tabs don't fit
+    ImGuiTabBarFlags_FittingPolicyMask_             = ImGuiTabBarFlags_FittingPolicyResizeDown | ImGuiTabBarFlags_FittingPolicyScroll,
+    ImGuiTabBarFlags_FittingPolicyDefault_          = ImGuiTabBarFlags_FittingPolicyResizeDown
+};  
+
+// Flags for ImGui::BeginTabItem()
+enum ImGuiTabItemFlags_
+{
+    ImGuiTabItemFlags_None                          = 0,
+    ImGuiTabItemFlags_UnsavedDocument               = 1 << 0,   // Append '*' to title without affecting the ID, as a convenience to avoid using the ### operator. Also: tab is selected on closure and closure is deferred by one frame to allow code to undo it without flicker.
+    ImGuiTabItemFlags_SetSelected                   = 1 << 1,   // Trigger flag to programatically make the tab selected when calling BeginTabItem()
+    ImGuiTabItemFlags_NoCloseWithMiddleMouseButton  = 1 << 2,   // Disable behavior of closing tabs (that are submitted with p_open != NULL) with middle mouse button. You can still repro this behavior on user's side with if (IsItemHovered() && IsMouseClicked(2)) *p_open = false.
+    ImGuiTabItemFlags_NoPushId                      = 1 << 3    // Don't call PushID(tab->ID)/PopID() on BeginTabItem()/EndTabItem()
+};
+
 // Flags for ImGui::IsWindowFocused()
 enum ImGuiFocusedFlags_
 {
@@ -956,6 +991,11 @@ enum ImGuiCol_
     ImGuiCol_ResizeGrip,
     ImGuiCol_ResizeGripHovered,
     ImGuiCol_ResizeGripActive,
+    ImGuiCol_Tab,
+    ImGuiCol_TabHovered,
+    ImGuiCol_TabActive,
+    ImGuiCol_TabUnfocused,
+    ImGuiCol_TabUnfocusedActive,
     ImGuiCol_PlotLines,
     ImGuiCol_PlotLinesHovered,
     ImGuiCol_PlotHistogram,
@@ -1003,6 +1043,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_ScrollbarRounding,   // float     ScrollbarRounding
     ImGuiStyleVar_GrabMinSize,         // float     GrabMinSize
     ImGuiStyleVar_GrabRounding,        // float     GrabRounding
+    ImGuiStyleVar_TabRounding,         // float     TabRounding
     ImGuiStyleVar_ButtonTextAlign,     // ImVec2    ButtonTextAlign
     ImGuiStyleVar_COUNT
 
@@ -1114,6 +1155,8 @@ struct ImGuiStyle
     float       ScrollbarRounding;          // Radius of grab corners for scrollbar.
     float       GrabMinSize;                // Minimum width/height of a grab box for slider/scrollbar.
     float       GrabRounding;               // Radius of grabs corners rounding. Set to 0.0f to have rectangular slider grabs.
+    float       TabRounding;                // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
+    float       TabBorderSize;              // Thickness of border around tabs. 
     ImVec2      ButtonTextAlign;            // Alignment of button text when button is larger than text. Defaults to (0.5f,0.5f) for horizontally+vertically centered.
     ImVec2      DisplayWindowPadding;       // Window position are clamped to be visible within the display area by at least this amount. Only applies to regular windows.
     ImVec2      DisplaySafeAreaPadding;     // If you cannot see the edges of your screen (e.g. on a TV) increase the safe area padding. Apply to popups/tooltips as well regular windows. NB: Prefer configuring your TV sets correctly!