Added io.ConfigWindowsMoveFromTitleBarOnly option. Still is ignored by window with no title bars (often popups). This affects clamping window within the visible area: with this option enabled title bars need to be visible. (#899)

Tweaked default value of style.DisplayWindowPadding from (20,20) to (19,19) so the default style as a value which is the same as the title bar height.

docs/CHANGELOG.txt

@@ -39,10 +39,14 @@ Breaking Changes:
   The addition of new configuration options in the Docking branch is pushing for a little reorganization of those names.
 
 Other Changes:
-- Examples: DirectX10/11/12: Made imgui_impl_dx10/dx11/dx12.cpp link d3dcompiler.lib from the .cpp file
-  to ease integration.
 - Resizing windows from edge is now enabled by default (io.ConfigWindowsResizeFromEdges=true). Note that 
   it only works _if_ the back-end sets ImGuiBackendFlags_HasMouseCursors, which the standard back-end do.
+- Added io.ConfigWindowsMoveFromTitleBarOnly option. Still is ignored by window with no title bars (often popups).
+  This affects clamping window within the visible area: with this option enabled title bars need to be visible. (#899)
+- Style: Tweaked default value of style.DisplayWindowPadding from (20,20) to (19,19) so the default style as a value
+  which is the same as the title bar height.
+- Examples: DirectX10/11/12: Made imgui_impl_dx10/dx11/dx12.cpp link d3dcompiler.lib from the .cpp file
+  to ease integration.
 
 
 -----------------------------------------------------------------------

imgui.cpp

@@ -1016,7 +1016,7 @@ ImGuiStyle::ImGuiStyle()
     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.
     ButtonTextAlign         = ImVec2(0.5f,0.5f);// Alignment of button text when button is larger than text.
-    DisplayWindowPadding    = ImVec2(20,20);    // Window position are clamped to be visible within the display area by at least this amount. Only applies to regular windows.
+    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.
     MouseCursorScale        = 1.0f;             // Scale software rendered mouse cursor (when io.MouseDrawCursor is enabled). May be removed later.
     AntiAliasedLines        = true;             // Enable anti-aliasing on lines/borders. Disable if you are really short on CPU/GPU.
@@ -1088,6 +1088,7 @@ ImGuiIO::ImGuiIO()
 #endif
     ConfigInputTextCursorBlink = true;
     ConfigWindowsResizeFromEdges = true;
+    ConfigWindowsMoveFromTitleBarOnly = false;
 
     // Platform Functions
     BackendPlatformName = BackendRendererName = NULL;
@@ -2906,6 +2907,8 @@ ImDrawListSharedData* ImGui::GetDrawListSharedData()
 void ImGui::StartMouseMovingWindow(ImGuiWindow* window)
 {
     // Set ActiveId even if the _NoMove flag is set. Without it, dragging away from a window with _NoMove would activate hover on other windows.
+    // We _also_ call this when clicking in a window empty space when io.ConfigWindowsMoveFromTitleBarOnly is set, but clear g.MovingWindow afterward.
+    // This is because we want ActiveId to be set even when the window is stuck from moving.
     ImGuiContext& g = *GImGui;
     FocusWindow(window);
     SetActiveID(window->MoveId, window);
@@ -3571,10 +3574,17 @@ void ImGui::EndFrame()
             if (g.IO.MouseClicked[0])
             {
                 if (g.HoveredRootWindow != NULL)
+                {
                     StartMouseMovingWindow(g.HoveredWindow);
+                    if (g.IO.ConfigWindowsMoveFromTitleBarOnly && !(g.HoveredRootWindow->Flags & ImGuiWindowFlags_NoTitleBar))
+                        if (!g.HoveredRootWindow->TitleBarRect().Contains(g.IO.MouseClickedPos[0]))
+                            g.MovingWindow = NULL;
+                }
                 else if (g.NavWindow != NULL && GetFrontMostPopupModal() == NULL)
+                {
                     FocusWindow(NULL);  // Clicking on void disable focus
                 }
+            }
 
             // With right mouse button we close popups without changing focus
             // (The left mouse button path calls FocusWindow which will lead NewFrame->ClosePopupsOverWindow to trigger)
@@ -4832,7 +4842,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             if (!window_pos_set_by_api && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0 && g.IO.DisplaySize.x > 0.0f && g.IO.DisplaySize.y > 0.0f) // Ignore zero-sized display explicitly to avoid losing positions if a window manager reports zero-sized window when initializing or minimizing.
             {
                 ImVec2 padding = ImMax(style.DisplayWindowPadding, style.DisplaySafeAreaPadding);
-                window->Pos = ImMax(window->Pos + window->Size, padding) - window->Size;
+                ImVec2 size_for_clamping = ((g.IO.ConfigWindowsMoveFromTitleBarOnly) && !(window->Flags & ImGuiWindowFlags_NoTitleBar)) ? ImVec2(window->Size.x, window->TitleBarHeight()) : window->Size;
+                window->Pos = ImMax(window->Pos + size_for_clamping, padding) - size_for_clamping;
                 window->Pos = ImMin(window->Pos, g.IO.DisplaySize - padding);
             }
         }

imgui.h

@@ -1166,6 +1166,7 @@ struct ImGuiIO
     bool          ConfigMacOSXBehaviors;            // = defined(__APPLE__) // OS X style: Text editing cursor movement using Alt instead of Ctrl, Shortcuts using Cmd/Super instead of Ctrl, Line/Text Start and End using Cmd+Arrows instead of Home/End, Double click selects by word instead of selecting whole text, Multi-selection in lists uses Cmd/Super instead of Ctrl (was called io.OptMacOSXBehaviors prior to 1.63)
     bool          ConfigInputTextCursorBlink;       // = true       // Set to false to disable blinking cursor, for users who consider it distracting. (was called: io.OptCursorBlink prior to 1.63)
     bool          ConfigWindowsResizeFromEdges;     // = true       // Enable resizing of windows from their edges and from the lower-left corner. This requires (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors) because it needs mouse cursor feedback. (This used to be the a per-window ImGuiWindowFlags_ResizeFromAnySide flag)
+    bool          ConfigWindowsMoveFromTitleBarOnly;// = false      // [BETA] Set to true to only allow moving windows when clicked+dragged from the title bar. Windows without a title bar are not affected.
 
     //------------------------------------------------------------------
     // Platform Functions

imgui_demo.cpp

@@ -318,6 +318,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::SameLine(); ShowHelpMarker("Set to false to disable blinking cursor, for users who consider it distracting");
             ImGui::Checkbox("io.ConfigWindowsResizeFromEdges", &io.ConfigWindowsResizeFromEdges);
             ImGui::SameLine(); ShowHelpMarker("Enable resizing of windows from their edges and from the lower-left corner.\nThis requires (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors) because it needs mouse cursor feedback.");
+            ImGui::Checkbox("io.ConfigWindowsMoveFromTitleBarOnly", &io.ConfigWindowsMoveFromTitleBarOnly);
             ImGui::Checkbox("io.MouseDrawCursor", &io.MouseDrawCursor);
             ImGui::SameLine(); ShowHelpMarker("Instruct Dear ImGui to render a mouse cursor for you. Note that a mouse cursor rendered via your application GPU rendering path will feel more laggy than hardware cursor, but will be more in sync with your other visuals.\n\nSome desktop applications may use both kinds of cursors (e.g. enable software cursor only when resizing/dragging something).");
             ImGui::TreePop();
@@ -2545,6 +2546,7 @@ void ImGui::ShowAboutWindow(bool* p_open)
         if (io.ConfigMacOSXBehaviors)                                   ImGui::Text("io.ConfigMacOSXBehaviors");
         if (io.ConfigInputTextCursorBlink)                              ImGui::Text("io.ConfigInputTextCursorBlink");
         if (io.ConfigWindowsResizeFromEdges)                            ImGui::Text("io.ConfigWindowsResizeFromEdges");
+        if (io.ConfigWindowsMoveFromTitleBarOnly)                       ImGui::Text("io.ConfigWindowsMoveFromTitleBarOnly");
         ImGui::Text("io.BackendFlags: 0x%08X", io.BackendFlags);
         if (io.BackendFlags & ImGuiBackendFlags_HasGamepad)             ImGui::Text(" HasGamepad");
         if (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors)        ImGui::Text(" HasMouseCursors");