Add possibility to pick colors from the desktop (fix #594)

Requested several times (e.g. https://community.aseprite.org/t/2431)

Added support only for Windows and macOS at the moment.

laf

@@ -1 +1 @@
-Subproject commit 410da165bde1e7353eb46aa58481a956f2ad489b
+Subproject commit 0b2e8b7a401aa34c245afe5e0114a498d4e341cd

src/app/ui/color_button.cpp

@@ -27,6 +27,8 @@
 #include "doc/layer.h"
 #include "doc/sprite.h"
 #include "gfx/rect_io.h"
+#include "os/system.h"
+#include "os/window.h"
 #include "ui/ui.h"
 
 #include <algorithm>
@@ -145,14 +147,50 @@ bool ColorButton::onProcessMessage(Message* msg)
     case kMouseMoveMessage:
       if (hasCapture()) {
         gfx::Point mousePos = static_cast<MouseMessage*>(msg)->position();
-        Widget* picked = manager()->pick(mousePos);
         app::Color color = m_color;
 
-        if (picked && picked != this) {
-          // Pick a color from a IColorSource
-          if (IColorSource* colorSource = dynamic_cast<IColorSource*>(picked)) {
-            color = colorSource->getColorByPosition(mousePos);
+        // Pick a color from a IColorSource
+        Widget* picked = window()->pick(mousePos);
+        IColorSource* colorSource = (picked != this ? dynamic_cast<IColorSource*>(picked): nullptr);
+
+        // If there is no color source, get the color from the display
+        // surface, and finally from the desktop. The desktop must be
+        // a last resource method, because in macOS it will ask for
+        // permissions to record the screen.
+        if (!colorSource) {
+          os::Window* nativeWindow = display()->nativeWindow();
+          gfx::Point screenPos = nativeWindow->pointToScreen(mousePos);
+
+          picked = manager()->pickFromScreenPos(screenPos);
+          colorSource = (picked != this ? dynamic_cast<IColorSource*>(picked): nullptr);
+          if (colorSource) {
+            nativeWindow = picked->display()->nativeWindow();
+            mousePos = nativeWindow->pointFromScreen(screenPos);
           }
+          else {
+            gfx::Color gfxColor = gfx::ColorNone;
+
+            // Get color from native window surface
+            if (nativeWindow->contentRect().contains(screenPos)) {
+              mousePos = nativeWindow->pointFromScreen(screenPos);
+              if (nativeWindow->surface()->bounds().contains(mousePos))
+                gfxColor = nativeWindow->surface()->getPixel(mousePos.x, mousePos.y);
+            }
+
+            // Or get the color from the screen
+            if (gfxColor == gfx::ColorNone) {
+              gfxColor = os::instance()->getColorFromScreen(screenPos);
+            }
+
+            color = app::Color::fromRgb(gfx::getr(gfxColor),
+                                        gfx::getg(gfxColor),
+                                        gfx::getb(gfxColor),
+                                        gfx::geta(gfxColor));
+          }
+        }
+
+        if (colorSource) {
+          color = colorSource->getColorByPosition(mousePos);
         }
 
         // Did the color change?

src/ui/manager.cpp

@@ -1118,6 +1118,11 @@ bool Manager::isFocusMovementMessage(Message* msg)
   return false;
 }
 
+Widget* Manager::pickFromScreenPos(const gfx::Point& screenPos) const
+{
+  return pick(gfx::Point(screenPos) - display()->nativeWindow()->contentRect().origin());
+}
+
 // Configures the window for begin the loop
 void Manager::_openWindow(Window* window)
 {

src/ui/manager.h

@@ -36,7 +36,7 @@ namespace ui {
     Manager(const os::WindowRef& nativeWindow);
     ~Manager();
 
-    Display* display() { return &m_display; }
+    Display* display() const { return &const_cast<Manager*>(this)->m_display; }
     Display* getDisplayFromNativeWindow(os::Window* window) const;
 
     // Executes the main message loop.
@@ -89,6 +89,8 @@ namespace ui {
     bool isFocusMovementMessage(Message* msg);
     bool processFocusMovementMessage(Message* msg);
 
+    Widget* pickFromScreenPos(const gfx::Point& screenPos) const;
+
     void _openWindow(Window* window);
     void _closeWindow(Window* window, bool redraw_background);