WindowServer: Add a "scale" parameter to the SetResolution message and plumb it through

Now, `chres 640 480 2` can set the UI to HighDPI 640x480 at runtime. A
real GUI for changing the display factor will come later.

(`chres 640 480 2` followed by `chres 1280 960` is very fast since
we don't have to re-allocate the framebuffer since both modes use
the exact same number of physical pixels.)

Userland/Applications/DisplaySettings/DisplaySettings.cpp

@@ -246,7 +246,8 @@ void DisplaySettingsWidget::load_current_settings()
 
 void DisplaySettingsWidget::send_settings_to_window_server()
 {
-    auto result = GUI::WindowServerConnection::the().send_sync<Messages::WindowServer::SetResolution>(m_monitor_widget->desktop_resolution());
+    // FIXME: Add UI for changing the scale factor.
+    auto result = GUI::WindowServerConnection::the().send_sync<Messages::WindowServer::SetResolution>(m_monitor_widget->desktop_resolution(), 1);
     if (!result->success()) {
         GUI::MessageBox::show(nullptr, String::formatted("Reverting to resolution {}x{}", result->resolution().width(), result->resolution().height()),
             "Unable to set resolution", GUI::MessageBox::Type::Error);

Userland/Services/WindowServer/ClientConnection.cpp

@@ -340,7 +340,7 @@ OwnPtr<Messages::WindowServer::GetWallpaperResponse> ClientConnection::handle(co
 
 OwnPtr<Messages::WindowServer::SetResolutionResponse> ClientConnection::handle(const Messages::WindowServer::SetResolution& message)
 {
-    return make<Messages::WindowServer::SetResolutionResponse>(WindowManager::the().set_resolution(message.resolution().width(), message.resolution().height()), WindowManager::the().resolution());
+    return make<Messages::WindowServer::SetResolutionResponse>(WindowManager::the().set_resolution(message.resolution().width(), message.resolution().height(), message.scale_factor()), WindowManager::the().resolution(), WindowManager::the().scale_factor());
 }
 
 OwnPtr<Messages::WindowServer::SetWindowTitleResponse> ClientConnection::handle(const Messages::WindowServer::SetWindowTitle& message)

Userland/Services/WindowServer/Compositor.cpp

@@ -710,19 +710,19 @@ void Compositor::run_animations(Gfx::DisjointRectSet& flush_rects)
     });
 }
 
-bool Compositor::set_resolution(int desired_width, int desired_height)
+bool Compositor::set_resolution(int desired_width, int desired_height, int scale_factor)
 {
     auto screen_rect = Screen::the().rect();
-    if (screen_rect.width() == desired_width && screen_rect.height() == desired_height)
+    if (screen_rect.width() == desired_width && screen_rect.height() == desired_height && Screen::the().scale_factor() == scale_factor)
         return true;
 
     // Make sure it's impossible to set an invalid resolution
-    if (!(desired_width >= 640 && desired_height >= 480)) {
-        dbg() << "Compositor: Tried to set invalid resolution: " << desired_width << "x" << desired_height;
+    if (!(desired_width >= 640 && desired_height >= 480 && scale_factor >= 1)) {
+        dbg() << "Compositor: Tried to set invalid resolution: " << desired_width << "x" << desired_height << " @ " << scale_factor << "x";
         return false;
     }
 
-    bool success = Screen::the().set_resolution(desired_width, desired_height, 1);
+    bool success = Screen::the().set_resolution(desired_width, desired_height, scale_factor);
     init_bitmaps();
     invalidate_occlusions();
     compose();

Userland/Services/WindowServer/Compositor.h

@@ -57,7 +57,7 @@ public:
     void invalidate_screen();
     void invalidate_screen(const Gfx::IntRect&);
 
-    bool set_resolution(int desired_width, int desired_height);
+    bool set_resolution(int desired_width, int desired_height, int scale_factor);
 
     bool set_background_color(const String& background_color);
 

Userland/Services/WindowServer/Screen.cpp

@@ -69,43 +69,53 @@ Screen::~Screen()
     close(m_framebuffer_fd);
 }
 
-bool Screen::set_resolution(int width, int height, int scale_factor)
+bool Screen::set_resolution(int width, int height, int new_scale_factor)
 {
-    FBResolution physical_resolution { 0, (unsigned)(width * scale_factor), (unsigned)(height * scale_factor) };
+    int new_physical_width = width * new_scale_factor;
+    int new_physical_height = height * new_scale_factor;
+    if (physical_width() == new_physical_width && physical_height() == new_physical_height) {
+        assert(scale_factor() != new_scale_factor);
+        on_change_resolution(m_pitch, physical_width(), physical_height(), new_scale_factor);
+        return true;
+    }
+
+    FBResolution physical_resolution { 0, (unsigned)new_physical_width, (unsigned)new_physical_height };
     int rc = fb_set_resolution(m_framebuffer_fd, &physical_resolution);
 #ifdef WSSCREEN_DEBUG
     dbg() << "fb_set_resolution() - return code " << rc;
 #endif
     if (rc == 0) {
-        on_change_resolution(physical_resolution.pitch, physical_resolution.width, physical_resolution.height, scale_factor);
+        on_change_resolution(physical_resolution.pitch, physical_resolution.width, physical_resolution.height, new_scale_factor);
         return true;
     }
     if (rc == -1) {
         dbg() << "Invalid resolution " << width << "x" << height;
-        on_change_resolution(physical_resolution.pitch, physical_resolution.width, physical_resolution.height, scale_factor);
+        on_change_resolution(physical_resolution.pitch, physical_resolution.width, physical_resolution.height, new_scale_factor);
         return false;
     }
     ASSERT_NOT_REACHED();
 }
 
-void Screen::on_change_resolution(int pitch, int physical_width, int physical_height, int scale_factor)
+void Screen::on_change_resolution(int pitch, int new_physical_width, int new_physical_height, int new_scale_factor)
 {
-    if (m_framebuffer) {
-        size_t previous_size_in_bytes = m_size_in_bytes;
-        int rc = munmap(m_framebuffer, previous_size_in_bytes);
+    if (physical_width() != new_physical_width || physical_height() != new_physical_height) {
+        if (m_framebuffer) {
+            size_t previous_size_in_bytes = m_size_in_bytes;
+            int rc = munmap(m_framebuffer, previous_size_in_bytes);
+            ASSERT(rc == 0);
+        }
+
+        int rc = fb_get_size_in_bytes(m_framebuffer_fd, &m_size_in_bytes);
         ASSERT(rc == 0);
+
+        m_framebuffer = (Gfx::RGBA32*)mmap(nullptr, m_size_in_bytes, PROT_READ | PROT_WRITE, MAP_SHARED, m_framebuffer_fd, 0);
+        ASSERT(m_framebuffer && m_framebuffer != (void*)-1);
     }
 
-    int rc = fb_get_size_in_bytes(m_framebuffer_fd, &m_size_in_bytes);
-    ASSERT(rc == 0);
-
-    m_framebuffer = (Gfx::RGBA32*)mmap(nullptr, m_size_in_bytes, PROT_READ | PROT_WRITE, MAP_SHARED, m_framebuffer_fd, 0);
-    ASSERT(m_framebuffer && m_framebuffer != (void*)-1);
-
     m_pitch = pitch;
-    m_width = physical_width / scale_factor;
-    m_height = physical_height / scale_factor;
-    m_scale_factor = scale_factor;
+    m_width = new_physical_width / new_scale_factor;
+    m_height = new_physical_height / new_scale_factor;
+    m_scale_factor = new_scale_factor;
 
     m_physical_cursor_location.constrain(physical_rect());
 }

Userland/Services/WindowServer/WindowManager.cpp

@@ -124,9 +124,9 @@ const Gfx::Font& WindowManager::window_title_font() const
     return Gfx::FontDatabase::default_bold_font();
 }
 
-bool WindowManager::set_resolution(int width, int height)
+bool WindowManager::set_resolution(int width, int height, int scale)
 {
-    bool success = Compositor::the().set_resolution(width, height);
+    bool success = Compositor::the().set_resolution(width, height, scale);
     MenuManager::the().set_needs_window_resize();
     ClientConnection::for_each_client([&](ClientConnection& client) {
         client.notify_about_new_screen_rect(Screen::the().rect());
@@ -139,14 +139,16 @@ bool WindowManager::set_resolution(int width, int height)
     }
     if (m_config) {
         if (success) {
-            dbg() << "Saving resolution: " << Gfx::IntSize(width, height) << " to config file at " << m_config->file_name();
+            dbg() << "Saving resolution: " << Gfx::IntSize(width, height) << " @ " << scale << "x to config file at " << m_config->file_name();
             m_config->write_num_entry("Screen", "Width", width);
             m_config->write_num_entry("Screen", "Height", height);
+            m_config->write_num_entry("Screen", "ScaleFactor", scale);
             m_config->sync();
         } else {
-            dbg() << "Saving fallback resolution: " << resolution() << " to config file at " << m_config->file_name();
+            dbg() << "Saving fallback resolution: " << resolution() << " @ 1x to config file at " << m_config->file_name();
             m_config->write_num_entry("Screen", "Width", resolution().width());
             m_config->write_num_entry("Screen", "Height", resolution().height());
+            m_config->write_num_entry("Screen", "ScaleFactor", 1);
             m_config->sync();
         }
     }
@@ -174,6 +176,11 @@ void WindowManager::set_scroll_step_size(unsigned step_size)
     m_config->sync();
 }
 
+int WindowManager::scale_factor() const
+{
+    return Screen::the().scale_factor();
+}
+
 void WindowManager::add_window(Window& window)
 {
     bool is_first_window = m_windows_in_order.is_empty();

Userland/Services/WindowServer/WindowManager.h

@@ -142,8 +142,9 @@ public:
     const Gfx::Font& font() const;
     const Gfx::Font& window_title_font() const;
 
-    bool set_resolution(int width, int height);
+    bool set_resolution(int width, int height, int scale);
     Gfx::IntSize resolution() const;
+    int scale_factor() const;
 
     void set_acceleration_factor(double);
     void set_scroll_step_size(unsigned);

Userland/Services/WindowServer/WindowServer.ipc

@@ -87,7 +87,7 @@ endpoint WindowServer = 2
     SetBackgroundColor(String background_color)  => ()
     SetWallpaperMode(String mode)  => ()
 
-    SetResolution(Gfx::IntSize resolution) => (bool success, Gfx::IntSize resolution)
+    SetResolution(Gfx::IntSize resolution, int scale_factor) => (bool success, Gfx::IntSize resolution, int scale_factor)
     SetWindowIconBitmap(i32 window_id, Gfx::ShareableBitmap icon) => ()
 
     GetWallpaper() => (String path)

Userland/Utilities/chres.cpp

@@ -32,17 +32,19 @@ int main(int argc, char** argv)
 {
     int width = -1;
     int height = -1;
+    int scale = 1;
 
     Core::ArgsParser args_parser;
     args_parser.set_general_help("Change the screen resolution.");
     args_parser.add_positional_argument(width, "Width", "width");
     args_parser.add_positional_argument(height, "Height", "height");
+    args_parser.add_positional_argument(scale, "Scale Factor", "scale", Core::ArgsParser::Required::No);
     args_parser.parse(argc, argv);
 
     // A Core::EventLoop is all we need, but WindowServerConnection needs a full Application object.
     char* dummy_argv[] = { argv[0] };
     auto app = GUI::Application::construct(1, dummy_argv);
-    auto result = GUI::WindowServerConnection::the().send_sync<Messages::WindowServer::SetResolution>(Gfx::IntSize { width, height });
+    auto result = GUI::WindowServerConnection::the().send_sync<Messages::WindowServer::SetResolution>(Gfx::IntSize { width, height }, scale);
     if (!result->success()) {
         warnln("failed to set resolution");
         return 1;