Windows: make Ctrl/+/-/0/ scaling system-wide if all screens have same DPI

5 files changed, 32 insertions, 8 deletions

diff --git a/src/Fl.cxx b/src/Fl.cxx
index c9a2972d2..dcf4be3bc 100644
--- a/src/Fl.cxx
+++ b/src/Fl.cxx
@@ -2266,8 +2266,13 @@ float Fl::screen_scale(int n) {
  Also sets the scale factor value of all windows mapped to screen number \p n, if any.
  */
 void Fl::screen_scale(int n, float factor) {
-  if (!Fl::screen_scaling_supported() || n < 0 || n >= Fl::screen_count()) return;
-  Fl::screen_driver()->rescale_all_windows_from_screen(n, factor);
+  Fl_Screen_Driver::APP_SCALING_CAPABILITY capability = Fl::screen_driver()->rescalable();
+  if (!capability || n < 0 || n >= Fl::screen_count()) return;
+  if (capability == Fl_Screen_Driver::SYSTEMWIDE_APP_SCALING) {
+    for (int s = 0; s < Fl::screen_count(); s++) {
+      Fl::screen_driver()->rescale_all_windows_from_screen(s, factor);
+    }
+  } else Fl::screen_driver()->rescale_all_windows_from_screen(n, factor);
 }
 
 /**
diff --git a/src/Fl_Screen_Driver.cxx b/src/Fl_Screen_Driver.cxx
index 623db30f6..fbb4aa4c2 100644
--- a/src/Fl_Screen_Driver.cxx
+++ b/src/Fl_Screen_Driver.cxx
@@ -386,8 +386,7 @@ void Fl_Screen_Driver::rescale_all_windows_from_screen(int screen, float f)
   int i = 0, count = 0; // count top-level windows, except transient scale-displaying window
   Fl_Window *win = Fl::first_window();
   while (win) {
-    if (!win->parent() &&
-        (Fl_Window_Driver::driver(win)->screen_num() == screen || rescalable() == SYSTEMWIDE_APP_SCALING) &&
+    if (!win->parent() && (Fl_Window_Driver::driver(win)->screen_num() == screen) &&
         win->user_data() != &Fl_Screen_Driver::transient_scale_display) {
       count++;
     }
@@ -398,8 +397,7 @@ void Fl_Screen_Driver::rescale_all_windows_from_screen(int screen, float f)
   Fl_Window **win_array = new Fl_Window*[count];
   win = Fl::first_window(); // memorize all top-level windows
   while (win) {
-    if (!win->parent() &&
-        (Fl_Window_Driver::driver(win)->screen_num() == screen || rescalable() == SYSTEMWIDE_APP_SCALING) &&
+    if (!win->parent() && (Fl_Window_Driver::driver(win)->screen_num() == screen) &&
         win->user_data() != &Fl_Screen_Driver::transient_scale_display) {
       win_array[i++] = win;
     }
@@ -541,7 +539,13 @@ int Fl_Screen_Driver::scale_handler(int event)
       f = scaling_values[i];
     }
     if (f == old_f) return 1;
-    screen_dr->rescale_all_windows_from_screen(screen, f * initial_scale);
+    if (screen_dr->rescalable() == SYSTEMWIDE_APP_SCALING) {
+      for (int i = 0; i < Fl::screen_count(); i++) {
+        screen_dr->rescale_all_windows_from_screen(i, f * initial_scale);
+      }
+    } else {
+      screen_dr->rescale_all_windows_from_screen(screen, f * initial_scale);
+    }
     Fl_Screen_Driver::transient_scale_display(f, screen);
     Fl::handle(FL_ZOOM_EVENT, NULL);
     return 1;
diff --git a/src/Fl_win32.cxx b/src/Fl_win32.cxx
index a88a57c19..9aa564650 100644
--- a/src/Fl_win32.cxx
+++ b/src/Fl_win32.cxx
@@ -521,6 +521,16 @@ void Fl_WinAPI_Screen_Driver::open_display_platform() {
 }
 
 
+void Fl_WinAPI_Screen_Driver::update_scaling_capability() {
+  scaling_capability = SYSTEMWIDE_APP_SCALING;
+  for (int ns = 1; ns < screen_count(); ns++) {
+    if (scale(ns) != scale(0)) {
+      scaling_capability = PER_SCREEN_APP_SCALING;
+      break;
+    }
+  }
+}
+
 void Fl_WinAPI_Screen_Driver::desktop_scale_factor() {
   typedef HRESULT(WINAPI * GetDpiForMonitor_type)(HMONITOR, int, UINT *, UINT *);
   typedef HMONITOR(WINAPI * MonitorFromRect_type)(LPCRECT, DWORD);
@@ -544,6 +554,7 @@ void Fl_WinAPI_Screen_Driver::desktop_scale_factor() {
     scale(ns, dpiX / 96.f);
     // fprintf(LOG, "desktop_scale_factor ns=%d factor=%.2f dpi=%.1f\n", ns, scale(ns), dpi[ns][0]);
   }
+  update_scaling_capability();
 }
 
 
@@ -1207,6 +1218,7 @@ static LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lPar
           float old_f = float(r.right) / window->w();
           Fl::screen_driver()->scale(ns, f);
           Fl_Window_Driver::driver(window)->resize_after_scale_change(ns, old_f, f);
+          sd->update_scaling_capability();
         }
         return 0;
       }
diff --git a/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.H b/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.H
index 3bbd51d59..816b667f6 100644
--- a/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.H
+++ b/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.H
@@ -41,6 +41,8 @@ protected:
 
 public:
   float dpi[MAX_SCREENS][2];
+  enum APP_SCALING_CAPABILITY scaling_capability;
+  void update_scaling_capability();
   Fl_WinAPI_Screen_Driver();
   // --- display management
   int visual(int flags) FL_OVERRIDE;
@@ -72,7 +74,7 @@ public:
   void open_display_platform() FL_OVERRIDE;
   void offscreen_size(Fl_Offscreen off, int &width, int &height) FL_OVERRIDE;
   APP_SCALING_CAPABILITY rescalable() FL_OVERRIDE {
-    return PER_SCREEN_APP_SCALING;
+    return scaling_capability;
   }
   float scale(int n) FL_OVERRIDE {
     return scale_of_screen[n];
diff --git a/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx b/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
index 452815afb..83f8f8973 100644
--- a/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
+++ b/src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
@@ -48,6 +48,7 @@ static Fl_Text_Editor::Key_Binding extra_bindings[] =  {
 Fl_WinAPI_Screen_Driver::Fl_WinAPI_Screen_Driver() : Fl_Screen_Driver() {
   text_editor_extra_key_bindings =  extra_bindings;
   for (int i = 0; i < MAX_SCREENS; i++) scale_of_screen[i] = 1;
+  scaling_capability = SYSTEMWIDE_APP_SCALING;
 }
 
 int Fl_WinAPI_Screen_Driver::visual(int flags)