half display resolution

src/display.rs

@@ -5,10 +5,10 @@ use embassy_rp::{
 };
 use embassy_time::{Delay, Timer};
 use embedded_graphics::{
-    Drawable,
-    pixelcolor::{BinaryColor, Rgb555, Rgb565},
-    prelude::{Point, Primitive, RgbColor, Size},
-    primitives::{PrimitiveStyle, Rectangle, Triangle},
+    Drawable, Pixel,
+    pixelcolor::{Rgb565, raw::RawU16},
+    prelude::{DrawTarget, OriginDimensions, Point, Primitive, RawData, RgbColor, Size},
+    primitives::{PrimitiveStyle, Rectangle},
 };
 use embedded_hal_bus::spi::ExclusiveDevice;
 use st7365p_lcd::{Orientation, ST7365P};
@@ -32,15 +32,82 @@ pub async fn display_task(
     );
     display.init(&mut Delay).unwrap();
     display.set_orientation(&Orientation::Landscape).unwrap();
+    let mut virtual_display = VirtualDisplay::new(display, 320 / 2, 320 / 2);
 
     let thin_stroke = PrimitiveStyle::with_stroke(Rgb565::RED, 20);
 
     Rectangle::new(Point::new(10, 10), Size::new(100, 100))
         .into_styled(thin_stroke)
-        .draw(&mut display)
+        .draw(&mut virtual_display)
         .unwrap();
 
     loop {
         Timer::after_millis(500).await;
     }
 }
+
+/// simple abstraction over real display & resolution to reduce frame buffer size
+/// by cutting the resolution by 1/4
+struct VirtualDisplay {
+    display: ST7365P<
+        ExclusiveDevice<Spi<'static, SPI1, Blocking>, Output<'static>, Delay>,
+        Output<'static>,
+        Output<'static>,
+    >,
+    width: u32,
+    height: u32,
+}
+
+impl VirtualDisplay {
+    pub fn new(
+        display: ST7365P<
+            ExclusiveDevice<Spi<'static, SPI1, Blocking>, Output<'static>, Delay>,
+            Output<'static>,
+            Output<'static>,
+        >,
+        new_width: u32,
+        new_height: u32,
+    ) -> Self {
+        Self {
+            display,
+            width: new_width,
+            height: new_height,
+        }
+    }
+}
+
+impl DrawTarget for VirtualDisplay {
+    type Color = Rgb565;
+    type Error = ();
+
+    fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>
+    where
+        I: IntoIterator<Item = Pixel<Self::Color>>,
+    {
+        for Pixel(coord, color) in pixels.into_iter() {
+            // Check bounds on the *virtual* (already reduced) resolution
+            if coord.x >= 0
+                && coord.y >= 0
+                && coord.x < self.width as i32
+                && coord.y < self.height as i32
+            {
+                let px = coord.x as u16 * 2;
+                let py = coord.y as u16 * 2;
+                let raw_color = RawU16::from(color).into_inner();
+
+                // Draw the 2x2 block on the underlying hardware
+                self.display.set_pixel(px, py, raw_color)?;
+                self.display.set_pixel(px + 1, py, raw_color)?;
+                self.display.set_pixel(px, py + 1, raw_color)?;
+                self.display.set_pixel(px + 1, py + 1, raw_color)?;
+            }
+        }
+        Ok(())
+    }
+}
+
+impl OriginDimensions for VirtualDisplay {
+    fn size(&self) -> Size {
+        Size::new(self.width, self.height)
+    }
+}