Add ScreenScaler::from_canvas (fixes #269)

CHANGELOG.md

@@ -15,6 +15,7 @@ This project adheres to Semantic Versioning.
   behaviour. ([@fililip](https://github.com/fililip) in [#321](https://github.com/17cupsofcoffee/tetra/pull/321))
 * `ScreenScaler` now has `scale_factor` and sizing utility methods. ([@timerertim](https://github.com/timerertim)
   in [#327](https://github.com/17cupsofcoffee/tetra/pull/327))
+* `ScreenScaler` now has a `from_canvas` constructor. This can be used for greater control over the canvas that is used for scaling.
 
 ### Changed
 

src/graphics/scaling.rs

@@ -51,6 +51,30 @@ impl ScreenScaler {
         })
     }
 
+    /// Returns a new `ScreenScaler`, using the given canvas for drawing.
+    /// The mode will determine how the image is scaled to fit the screen.
+    pub fn from_canvas(
+        canvas: Canvas,
+        outer_width: i32,
+        outer_height: i32,
+        mode: ScalingMode,
+    ) -> Result<ScreenScaler> {
+        let (inner_width, inner_height) = canvas.size();
+
+        let screen_rect =
+            get_screen_rect(mode, inner_width, inner_height, outer_width, outer_height);
+
+        Ok(ScreenScaler {
+            canvas,
+            mode,
+            screen_rect,
+            inner_width,
+            inner_height,
+            outer_width,
+            outer_height,
+        })
+    }
+
     /// Returns a new `ScreenScaler`, with the specified inner width and height, and the outer
     /// size set to the current dimensions of the window.
     pub fn with_window_size(