Added Config::startDragDistance()

Allows the user to change the drag threshold without having
to inherit from Platform

Changelog

@@ -7,6 +7,7 @@
     - Non-gui logic moved to controllers
     - Each controller has a gui counter part, implemented for each supported frontend
   - Uses nlohmann JSON library (MIT) instead of QJsonDocument, for saving/restoring layouts
+  - Added Config::setStartDragDistance()
 
 * v1.6.0 (unreleased)
  - Fixed restoring of normal geometry when closing a maximized window (#259)

src/Config.cpp

@@ -56,6 +56,7 @@ public:
     CustomizableWidgets m_disabledPaintEvents = CustomizableWidget_None;
     qreal m_draggedWindowOpacity = Q_QNAN;
     int m_mdiPopupThreshold = 250;
+    int m_startDragDistance = -1;
     bool m_dropIndicatorsInhibited = false;
 };
 
@@ -309,4 +310,14 @@ bool Config::dropIndicatorsInhibited() const
     return d->m_dropIndicatorsInhibited;
 }
 
+void Config::setStartDragDistance(int pixels)
+{
+    d->m_startDragDistance = pixels;
+}
+
+int Config::startDragDistance() const
+{
+    return d->m_startDragDistance;
+}
+
 }

src/Config.h

@@ -86,7 +86,8 @@ public:
     ///@warning Only the default is supported on all platforms. Not all options work with all window managers,
     ///         Qt does its best to abstract the differences however that's only a best effort. This is true specially
     ///         for any option that changes window flags.
-    enum Flag {
+    enum Flag
+    {
         Flag_None = 0, ///< No option set
         Flag_NativeTitleBar = 1, ///< Enables the Native OS title bar on OSes that support it (Windows 10, macOS), ignored otherwise.
         Flag_AeroSnapWithClientDecos = 2, ///< Deprecated. This is now default and cannot be turned off. Moving a window on Windows 10 uses native moving, as that works well across screens with different HDPI settings. There's no reason to use manual client/Qt window moving.
@@ -113,7 +114,8 @@ public:
     Q_DECLARE_FLAGS(Flags, Flag)
 
     ///@brief List of customizable widgets
-    enum CustomizableWidget {
+    enum CustomizableWidget
+    {
         CustomizableWidget_None = 0, ///< None
         CustomizableWidget_TitleBar, ///< The title bar
         CustomizableWidget_DockWidget, ///< The dock widget
@@ -128,7 +130,8 @@ public:
     ///@internal
     /// Internal flags for additional tuning.
     ///@warning Not for public consumption, support will be limited.
-    enum InternalFlag {
+    enum InternalFlag
+    {
         InternalFlag_None = 0, ///< The default
         InternalFlag_NoAeroSnap = 1, ///< Only for development. Disables Aero-snap.
         InternalFlag_DontUseParentForFloatingWindows = 2, ///< FloatingWindows won't have a parent top-level.
@@ -319,6 +322,16 @@ public:
     void setMDIPopupThreshold(int);
     int mdiPopupThreshold() const;
 
+    /// @brief Sets how many pixels the mouse needs to travel before a drag is actually started
+    /// Calling this is usually unneeded and just provided as a means to override Platform::startDragDistance()
+    /// , which already has a reasonable default 4 pixels
+    void setStartDragDistance(int);
+
+    /// @brief Returns the value set by setStartDragDistance()
+    /// Returns -1 if setStartDragDistance() wasn't call, in which case the Platform::startDragDistance()
+    /// will be used
+    int startDragDistance() const;
+
 private:
     Q_DISABLE_COPY(Config)
     Config();

src/Platform.cpp

@@ -74,6 +74,16 @@ bool Platform::isQtQuick() const
 
 int Platform::startDragDistance() const
 {
+    const int userRequestedDistance = Config::self().startDragDistance();
+    if (userRequestedDistance > -1)
+        return userRequestedDistance;
+
+    return startDragDistance_impl();
+}
+
+int Platform::startDragDistance_impl() const
+{
+    // Override this method in derived classes for some different value if needed
     return 4;
 }
 

src/Platform.h

@@ -99,7 +99,10 @@ public:
     bool isQtQuick() const;
 
     /// @brief Returns how many pixels the mouse must move for a drag to start
-    virtual int startDragDistance() const;
+    /// This is usually 4 by default (QApplication::startDragDistance() for QtWidgets)
+    /// You can override by calling Config::setStartDragDistance(), so you don't need to create
+    /// a new Platform class.
+    int startDragDistance() const;
 
     /// @brief Return whether we use the global event filter based mouse grabber
     virtual bool usesFallbackMouseGrabber() const = 0;
@@ -255,6 +258,7 @@ public:
     Private *const d;
 
 protected:
+    virtual int startDragDistance_impl() const;
     Platform();
 };
 

src/qtwidgets/Platform_qtwidgets.cpp

@@ -162,7 +162,7 @@ QSize Platform_qtwidgets::screenSizeFor(View *view) const
     return {};
 }
 
-int Platform_qtwidgets::startDragDistance() const
+int Platform_qtwidgets::startDragDistance_impl() const
 {
     return QApplication::startDragDistance();
 }

src/qtwidgets/Platform_qtwidgets.h

@@ -37,7 +37,7 @@ public:
     int screenNumberFor(View *) const override;
     QSize screenSizeFor(View *) const override;
 
-    int startDragDistance() const override;
+    int startDragDistance_impl() const override;
     View *createView(View *parent = nullptr) const override;
     bool inDisallowedDragView(QPoint globalPos) const override;
     bool usesFallbackMouseGrabber() const override;

tests/tst_platform.cpp

@@ -12,6 +12,7 @@
 #include "main.h"
 #include "private/View_p.h"
 #include "Platform.h"
+#include "Config.h"
 
 #include <string>
 
@@ -32,4 +33,15 @@ TEST_CASE("Platform::createDefaultViewFactory")
 {
     auto plat = Platform::instance();
     REQUIRE(plat->createDefaultViewFactory());
-}
+}
+
+TEST_CASE("Platform::startDragDistance")
+{
+    auto plat = Platform::instance();
+    const int defaultDistance = plat->startDragDistance();
+    CHECK_GE(defaultDistance, -1);
+
+    const int newDistance = defaultDistance + 1;
+    Config::self().setStartDragDistance(newDistance);
+    CHECK_EQ(plat->startDragDistance(), newDistance);
+}