Refactor DPI scaling and fix the GTK implementation.

CHANGELOG.md

@@ -43,6 +43,8 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 - `Env` and `Key` gained methods for inspecting an `Env` at runtime ([#880] by [@Zarenor])
 - `UpdateCtx::request_timer` and `UpdateCtx::request_anim_frame`. ([#898] by [@finnerale])
 - `LifeCycleCtx::request_timer`. ([#954] by [@xStrom])
+- `scale` method to `WinHandler`. ([#904] by [@xStrom])
+- `WinHandler::scale` method to inform of scale changes. ([#904] by [@xStrom])
 - `UpdateCtx::size` and `LifeCycleCtx::size`. ([#917] by [@jneem])
 - `WidgetExt::debug_widget_id`, for displaying widget ids on hover. ([#876] by [@cmyr])
 - `im` feature, with `Data` support for the [`im` crate](https://docs.rs/im/) collections. ([#924] by [@cmyr])
@@ -61,6 +63,8 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 - Global `Application` associated functions are instance methods instead, e.g. `Application::global().quit()` instead of the old `Application::quit()`. ([#763] by [@xStrom])
 - Timer events will only be delivered to the widgets that requested them. ([#831] by [@sjoshid])
 - `Event::Wheel` now contains a `MouseEvent` structure. ([#895] by [@teddemunnik])
+- The `WindowHandle::get_dpi` method got replaced by `WindowHandle::get_scale`. ([#904] by [@xStrom])
+- The `WinHandler::size` method now gets a `Size` in display points. ([#904] by [@xStrom])
 - `AppDelegate::command` now receives a `Target` instead of a `&Target`. ([#909] by [@xStrom])
 - `SHOW_WINDOW` and `CLOSE_WINDOW` commands now only use `Target` to determine the affected window. ([#928] by [@finnerale])
 - Replaced `NEW_WINDOW`, `SET_MENU` and `SHOW_CONTEXT_MENU` commands with methods on `EventCtx` and `DelegateCtx`. ([#931] by [@finnerale])
@@ -94,6 +98,7 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 - X11: Support individual window closing. ([#900] by [@xStrom])
 - X11: Support `Application::quit`. ([#900] by [@xStrom])
 - GTK: Support file filters in open/save dialogs. ([#903] by [@jneem])
+- GTK: Support DPI values other than 96. ([#904] by [@xStrom])
 - X11: Support key and mouse button state. ([#920] by [@jneem])
 - Routing `LifeCycle::FocusChanged` to descendant widgets. ([#925] by [@yrns])
 - Built-in open and save menu items now show the correct label and submit the right commands. ([#930] by [@finnerale])
@@ -125,6 +130,7 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 - GTK: Refactored `Application` to use the new structure. ([#892] by [@xStrom])
 - X11: Refactored `Application` to use the new structure. ([#894] by [@xStrom])
 - X11: Refactored `Window` to support some reentrancy and invalidation. ([#894] by [@xStrom])
+- Refactored DPI scaling. ([#904] by [@xStrom])
 - Added docs generation testing for all features. ([#942] by [@xStrom])
 
 ### Outside News
@@ -183,6 +189,7 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 [#898]: https://github.com/xi-editor/druid/pull/898
 [#900]: https://github.com/xi-editor/druid/pull/900
 [#903]: https://github.com/xi-editor/druid/pull/903
+[#904]: https://github.com/xi-editor/druid/pull/904
 [#905]: https://github.com/xi-editor/druid/pull/905
 [#909]: https://github.com/xi-editor/druid/pull/909
 [#917]: https://github.com/xi-editor/druid/pull/917

docs/src/widget.md

@@ -48,7 +48,7 @@ widgets].
 
 Widgets are intended to be modular and composable, not monolithic. For instance,
 widgets generally do not control their own alignment or padding; if you have
-a label, and you would like it to have 8px of horizontal padding and 4px of
+a label, and you would like it to have 8dp of horizontal padding and 4dp of
 vertical padding, you can just do,
 
 ```rust,noplaypen

druid-shell/examples/invalidate.rs

@@ -16,14 +16,14 @@ use std::any::Any;
 
 use std::time::{Duration, Instant};
 
-use druid_shell::kurbo::{Point, Rect};
+use druid_shell::kurbo::{Point, Rect, Size};
 use druid_shell::piet::{Color, Piet, RenderContext};
 
 use druid_shell::{Application, TimerToken, WinHandler, WindowBuilder, WindowHandle};
 
 struct InvalidateTest {
     handle: WindowHandle,
-    size: (f64, f64),
+    size: Size,
     start_time: Instant,
     color: Color,
     rect: Rect,
@@ -39,10 +39,10 @@ impl InvalidateTest {
             (_, _) => Color::rgb8(r, g, b.wrapping_add(10)),
         };
 
-        self.rect.x0 = (self.rect.x0 + 5.0) % self.size.0;
-        self.rect.x1 = (self.rect.x1 + 5.5) % self.size.0;
-        self.rect.y0 = (self.rect.y0 + 3.0) % self.size.1;
-        self.rect.y1 = (self.rect.y1 + 3.5) % self.size.1;
+        self.rect.x0 = (self.rect.x0 + 5.0) % self.size.width;
+        self.rect.x1 = (self.rect.x1 + 5.5) % self.size.width;
+        self.rect.y0 = (self.rect.y0 + 3.0) % self.size.height;
+        self.rect.y1 = (self.rect.y1 + 3.5) % self.size.height;
     }
 }
 
@@ -63,12 +63,8 @@ impl WinHandler for InvalidateTest {
         false
     }
 
-    fn size(&mut self, width: u32, height: u32) {
-        let dpi = self.handle.get_dpi();
-        let dpi_scale = dpi as f64 / 96.0;
-        let width_f = (width as f64) / dpi_scale;
-        let height_f = (height as f64) / dpi_scale;
-        self.size = (width_f, height_f);
+    fn size(&mut self, size: Size) {
+        self.size = size;
     }
 
     fn command(&mut self, id: u32) {
@@ -91,7 +87,7 @@ fn main() {
     let app = Application::new().unwrap();
     let mut builder = WindowBuilder::new(app.clone());
     let inv_test = InvalidateTest {
-        size: Default::default(),
+        size: Size::ZERO,
         handle: Default::default(),
         start_time: Instant::now(),
         rect: Rect::from_origin_size(Point::ZERO, (10.0, 20.0)),

druid-shell/examples/perftest.rs

@@ -16,7 +16,7 @@ use std::any::Any;
 
 use time::Instant;
 
-use piet_common::kurbo::{Line, Rect};
+use piet_common::kurbo::{Line, Rect, Size};
 use piet_common::{Color, FontBuilder, Piet, RenderContext, Text, TextLayoutBuilder};
 
 use druid_shell::{Application, KeyEvent, WinHandler, WindowBuilder, WindowHandle};
@@ -26,7 +26,7 @@ const FG_COLOR: Color = Color::rgb8(0xf0, 0xf0, 0xea);
 
 struct PerfTest {
     handle: WindowHandle,
-    size: (f64, f64),
+    size: Size,
     start_time: Instant,
     last_time: Instant,
 }
@@ -37,11 +37,14 @@ impl WinHandler for PerfTest {
     }
 
     fn paint(&mut self, piet: &mut Piet, _: Rect) -> bool {
-        let (width, height) = self.size;
-        let rect = Rect::new(0.0, 0.0, width, height);
+        let rect = self.size.to_rect();
         piet.fill(rect, &BG_COLOR);
 
-        piet.stroke(Line::new((0.0, height), (width, 0.0)), &FG_COLOR, 1.0);
+        piet.stroke(
+            Line::new((0.0, self.size.height), (self.size.width, 0.0)),
+            &FG_COLOR,
+            1.0,
+        );
 
         let current_ns = (Instant::now() - self.start_time).whole_nanoseconds();
         let th = ::std::f64::consts::PI * (current_ns as f64) * 2e-9;
@@ -98,12 +101,8 @@ impl WinHandler for PerfTest {
         false
     }
 
-    fn size(&mut self, width: u32, height: u32) {
-        let dpi = self.handle.get_dpi();
-        let dpi_scale = dpi as f64 / 96.0;
-        let width_f = (width as f64) / dpi_scale;
-        let height_f = (height as f64) / dpi_scale;
-        self.size = (width_f, height_f);
+    fn size(&mut self, size: Size) {
+        self.size = size;
     }
 
     fn destroy(&mut self) {
@@ -119,7 +118,7 @@ fn main() {
     let app = Application::new().unwrap();
     let mut builder = WindowBuilder::new(app.clone());
     let perf_test = PerfTest {
-        size: Default::default(),
+        size: Size::ZERO,
         handle: Default::default(),
         start_time: time::Instant::now(),
         last_time: time::Instant::now(),

druid-shell/examples/shello.rs

@@ -14,7 +14,7 @@
 
 use std::any::Any;
 
-use druid_shell::kurbo::{Line, Rect};
+use druid_shell::kurbo::{Line, Rect, Size};
 use druid_shell::piet::{Color, RenderContext};
 
 use druid_shell::{
@@ -27,7 +27,7 @@ const FG_COLOR: Color = Color::rgb8(0xf0, 0xf0, 0xea);
 
 #[derive(Default)]
 struct HelloState {
-    size: (f64, f64),
+    size: Size,
     handle: WindowHandle,
 }
 
@@ -37,8 +37,7 @@ impl WinHandler for HelloState {
     }
 
     fn paint(&mut self, piet: &mut piet_common::Piet, _: Rect) -> bool {
-        let (width, height) = self.size;
-        let rect = Rect::new(0.0, 0.0, width, height);
+        let rect = self.size.to_rect();
         piet.fill(rect, &BG_COLOR);
         piet.stroke(Line::new((10.0, 50.0), (90.0, 90.0)), &FG_COLOR, 1.0);
         false
@@ -92,12 +91,8 @@ impl WinHandler for HelloState {
         println!("timer fired: {:?}", id);
     }
 
-    fn size(&mut self, width: u32, height: u32) {
-        let dpi = self.handle.get_dpi();
-        let dpi_scale = dpi as f64 / 96.0;
-        let width_f = (width as f64) / dpi_scale;
-        let height_f = (height as f64) / dpi_scale;
-        self.size = (width_f, height_f);
+    fn size(&mut self, size: Size) {
+        self.size = size;
     }
 
     fn destroy(&mut self) {

druid-shell/src/error.rs

@@ -18,13 +18,19 @@ use std::fmt;
 
 use crate::platform::error as platform;
 
-/// Error codes. At the moment, this is little more than HRESULT, but that
-/// might change.
+/// Shell errors.
 #[derive(Debug, Clone)]
 pub enum Error {
+    /// The Application instance has already been created.
     ApplicationAlreadyExists,
-    Other(&'static str),
+    /// The window has already been destroyed.
+    WindowDropped,
+    /// Runtime borrow failure.
+    BorrowError(BorrowError),
+    /// Platform specific error.
     Platform(platform::Error),
+    /// Other miscellaneous error.
+    Other(&'static str),
 }
 
 impl fmt::Display for Error {
@@ -33,8 +39,10 @@ impl fmt::Display for Error {
             Error::ApplicationAlreadyExists => {
                 write!(f, "An application instance has already been created.")
             }
+            Error::WindowDropped => write!(f, "The window has already been destroyed."),
+            Error::BorrowError(err) => fmt::Display::fmt(err, f),
+            Error::Platform(err) => fmt::Display::fmt(err, f),
             Error::Other(s) => write!(f, "{}", s),
-            Error::Platform(p) => fmt::Display::fmt(&p, f),
         }
     }
 }
@@ -46,3 +54,49 @@ impl From<platform::Error> for Error {
         Error::Platform(src)
     }
 }
+
+/// Runtime borrow failure.
+#[derive(Debug, Clone)]
+pub struct BorrowError {
+    location: &'static str,
+    target: &'static str,
+    mutable: bool,
+}
+
+impl BorrowError {
+    pub fn new(location: &'static str, target: &'static str, mutable: bool) -> BorrowError {
+        BorrowError {
+            location,
+            target,
+            mutable,
+        }
+    }
+}
+
+impl fmt::Display for BorrowError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        if self.mutable {
+            // Mutable borrow fails when any borrow exists
+            write!(
+                f,
+                "{} was already borrowed in {}",
+                self.target, self.location
+            )
+        } else {
+            // Regular borrow fails when a mutable borrow exists
+            write!(
+                f,
+                "{} was already mutably borrowed in {}",
+                self.target, self.location
+            )
+        }
+    }
+}
+
+impl std::error::Error for BorrowError {}
+
+impl From<BorrowError> for Error {
+    fn from(src: BorrowError) -> Error {
+        Error::BorrowError(src)
+    }
+}

druid-shell/src/lib.rs

@@ -35,6 +35,7 @@ mod keycodes;
 mod menu;
 mod mouse;
 mod platform;
+mod scale;
 mod util;
 mod window;
 
@@ -48,6 +49,7 @@ pub use keyboard::{KeyEvent, KeyModifiers};
 pub use keycodes::KeyCode;
 pub use menu::Menu;
 pub use mouse::{Cursor, MouseButton, MouseButtons, MouseEvent};
+pub use scale::{Scalable, Scale, ScaledArea};
 pub use window::{
     IdleHandle, IdleToken, Text, TimerToken, WinHandler, WindowBuilder, WindowHandle,
 };

druid-shell/src/mouse.rs

@@ -24,9 +24,9 @@ use crate::keyboard::KeyModifiers;
 /// receiving a move event before another mouse event.
 #[derive(Debug, Clone, PartialEq)]
 pub struct MouseEvent {
-    /// The location of the mouse in the current window.
+    /// The location of the mouse in [display points] in relation to the current window.
     ///
-    /// This is in px units not device pixels, that is, adjusted for hi-dpi.
+    /// [display points]: struct.Scale.html
     pub pos: Point,
     /// Mouse buttons being held down during a move or after a click event.
     /// Thus it will contain the `button` that triggered a mouse-down event,