Simplify Scale by removing DPI. (#1042)

CHANGELOG.md

@@ -12,11 +12,14 @@ You can find its changes [documented below](#060---2020-06-01).
 ### Changed
 
 - `Image` and `ImageData` exported by default. ([#1011] by [@covercash2])
+- `Scale::from_scale` to `Scale::new`, and `Scale` methods `scale_x` / `scale_y` to `x` / `y`. ([#1042] by [@xStrom])
 
 ### Deprecated
 
 ### Removed
 
+- `Scale::from_dpi`, `Scale::dpi_x`, and `Scale::dpi_y`. ([#1042] by [@xStrom])
+
 ### Fixed
 
 - macOS: Timers not firing during modal loop. ([#1028] by [@xStrom])
@@ -324,6 +327,7 @@ Last release without a changelog :(
 [#1011]: https://github.com/xi-editor/druid/pull/1011
 [#1013]: https://github.com/xi-editor/druid/pull/1013
 [#1028]: https://github.com/xi-editor/druid/pull/1028
+[#1042]: https://github.com/xi-editor/druid/pull/1042
 
 [Unreleased]: https://github.com/xi-editor/druid/compare/v0.6.0...master
 [0.6.0]: https://github.com/xi-editor/druid/compare/v0.5.0...v0.6.0

druid-shell/src/platform/gtk/window.rs

@@ -47,6 +47,11 @@ use super::dialog;
 use super::menu::Menu;
 use super::util;
 
+/// The platform target DPI.
+///
+/// GTK considers 96 the default value which represents a 1.0 scale factor.
+const SCALE_TARGET_DPI: f64 = 96.0;
+
 /// Taken from https://gtk-rs.org/docs-src/tutorial/closures
 /// It is used to reduce the boilerplate of setting up gtk callbacks
 /// Example:
@@ -169,12 +174,13 @@ impl WindowBuilder {
         window.set_resizable(self.resizable);
         window.set_decorated(self.show_titlebar);
 
-        // Get the GTK reported DPI
-        let dpi = window
+        // Get the scale factor based on the GTK reported DPI
+        let scale_factor = window
             .get_display()
-            .map(|c| c.get_default_screen().get_resolution() as f64)
-            .unwrap_or(96.0);
-        let scale = Scale::from_dpi(dpi, dpi);
+            .map(|c| c.get_default_screen().get_resolution())
+            .unwrap_or(SCALE_TARGET_DPI)
+            / SCALE_TARGET_DPI;
+        let scale = Scale::new(scale_factor, scale_factor);
         let area = ScaledArea::from_dp(self.size, &scale);
         let size_px = area.size_px();
 
@@ -254,9 +260,9 @@ impl WindowBuilder {
                 let mut scale_changed = false;
                 // Check if the GTK reported DPI has changed,
                 // so that we can change our scale factor without restarting the application.
-                if let Some(dpi) = state.window.get_window()
-                    .map(|w| w.get_display().get_default_screen().get_resolution()) {
-                    let reported_scale = Scale::from_dpi(dpi, dpi);
+                if let Some(scale_factor) = state.window.get_window()
+                    .map(|w| w.get_display().get_default_screen().get_resolution() / SCALE_TARGET_DPI) {
+                    let reported_scale = Scale::new(scale_factor, scale_factor);
                     if scale != reported_scale {
                         scale = reported_scale;
                         state.scale.set(scale);
@@ -286,7 +292,7 @@ impl WindowBuilder {
                 if let Ok(mut handler_borrow) = state.handler.try_borrow_mut() {
                     // For some reason piet needs a mutable context, so give it one I guess.
                     let mut context = context.clone();
-                    context.scale(scale.scale_x(), scale.scale_y());
+                    context.scale(scale.x(), scale.y());
                     let (x0, y0, x1, y1) = context.clip_extents();
                     let invalid_rect = Rect::new(x0, y0, x1, y1);
 

druid-shell/src/platform/mac/window.rs

@@ -884,7 +884,7 @@ impl WindowHandle {
     /// Get the `Scale` of the window.
     pub fn get_scale(&self) -> Result<Scale, Error> {
         // TODO: Get actual Scale
-        Ok(Scale::from_dpi(96.0, 96.0))
+        Ok(Scale::new(1.0, 1.0))
     }
 }
 

druid-shell/src/platform/web/window.rs

@@ -137,12 +137,12 @@ impl WindowState {
     /// Updates the canvas size and scale factor and returns `Scale` and `ScaledArea`.
     fn update_scale_and_area(&self) -> (Scale, ScaledArea) {
         let (css_width, css_height, dpr) = self.get_window_size_and_dpr();
-        let scale = Scale::from_scale(dpr, dpr);
+        let scale = Scale::new(dpr, dpr);
         let area = ScaledArea::from_dp(Size::new(css_width, css_height), &scale);
         let size_px = area.size_px();
         self.canvas.set_width(size_px.width as u32);
         self.canvas.set_height(size_px.height as u32);
-        let _ = self.context.scale(scale.scale_x(), scale.scale_y());
+        let _ = self.context.scale(scale.x(), scale.y());
         self.scale.set(scale);
         self.area.set(area);
         (scale, area)
@@ -373,7 +373,7 @@ impl WindowBuilder {
         // Create the Scale for resolution scaling
         let scale = {
             let dpr = window.device_pixel_ratio();
-            Scale::from_scale(dpr, dpr)
+            Scale::new(dpr, dpr)
         };
         let area = {
             // The initial size in display points isn't necessarily the final size in display points
@@ -383,7 +383,7 @@ impl WindowBuilder {
         let size_px = area.size_px();
         canvas.set_width(size_px.width as u32);
         canvas.set_height(size_px.height as u32);
-        let _ = context.scale(scale.scale_x(), scale.scale_y());
+        let _ = context.scale(scale.x(), scale.y());
         let size_dp = area.size_dp();
 
         set_cursor(&canvas, &self.cursor);

druid-shell/src/platform/windows/paint.rs

@@ -40,6 +40,7 @@ use crate::scale::Scale;
 
 use super::error::Error;
 use super::util::as_result;
+use super::window::SCALE_TARGET_DPI;
 
 pub(crate) unsafe fn create_render_target(
     d2d_factory: &D2DFactory,
@@ -82,8 +83,8 @@ pub(crate) unsafe fn create_render_target_dxgi(
             format: DXGI_FORMAT_B8G8R8A8_UNORM,
             alphaMode: D2D1_ALPHA_MODE_IGNORE,
         },
-        dpiX: scale.dpi_x() as f32,
-        dpiY: scale.dpi_y() as f32,
+        dpiX: (scale.x() * SCALE_TARGET_DPI) as f32,
+        dpiY: (scale.y() * SCALE_TARGET_DPI) as f32,
         usage: D2D1_RENDER_TARGET_USAGE_NONE,
         minLevel: D2D1_FEATURE_LEVEL_DEFAULT,
     };

druid-shell/src/platform/windows/window.rs

@@ -65,6 +65,11 @@ use crate::mouse::{Cursor, MouseButton, MouseButtons, MouseEvent};
 use crate::scale::{Scale, ScaledArea};
 use crate::window::{IdleToken, Text, TimerToken, WinHandler};
 
+/// The platform target DPI.
+///
+/// Windows considers 96 the default value which represents a 1.0 scale factor.
+pub(crate) const SCALE_TARGET_DPI: f64 = 96.0;
+
 extern "system" {
     pub fn DwmFlush();
 }
@@ -1026,16 +1031,16 @@ impl WindowBuilder {
                 present_strategy: self.present_strategy,
             };
 
-            // Simple scaling based on System DPI (96 is equivalent to 100%)
-            let dpi = if let Some(func) = OPTIONAL_FUNCTIONS.GetDpiForSystem {
+            // Simple scaling based on System DPI
+            let scale_factor = if let Some(func) = OPTIONAL_FUNCTIONS.GetDpiForSystem {
                 // Only supported on Windows 10
-                func() as f64
+                func() as f64 / SCALE_TARGET_DPI
             } else {
                 // TODO GetDpiForMonitor is supported on Windows 8.1, try falling back to that here
                 // Probably GetDeviceCaps(..., LOGPIXELSX) is the best to do pre-10
-                96.0
+                1.0
             };
-            let scale = Scale::from_dpi(dpi, dpi);
+            let scale = Scale::new(scale_factor, scale_factor);
             let area = ScaledArea::from_dp(self.size, &scale);
             let size_px = area.size_px();
 

druid-shell/src/platform/x11/window.rs

@@ -476,7 +476,7 @@ impl Window {
 
     fn get_scale(&self) -> Result<Scale, Error> {
         // TODO(x11/dpi_scaling): figure out DPI scaling
-        Ok(Scale::from_dpi(96.0, 96.0))
+        Ok(Scale::new(1.0, 1.0))
     }
 
     pub fn handle_expose(&self, expose: &xcb::ExposeEvent) -> Result<(), Error> {
@@ -820,7 +820,7 @@ impl WindowHandle {
             Ok(w.get_scale()?)
         } else {
             log::error!("Window {} has already been dropped", self.id);
-            Ok(Scale::from_dpi(96.0, 96.0))
+            Ok(Scale::new(1.0, 1.0))
         }
     }
 }