Get pixel and documentation of public functions

.gitignore

@@ -1 +1,2 @@
 /target
+/temp

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "chinchilib"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 license-file = "LICENSE.txt"
 description = "A graphical prototyping library for my students"

README.md

@@ -6,6 +6,24 @@ It's mostly a wrapper arround pixels and winit that takes care of refresh rate,
 
 # Usage
 
+`chinchilib` exposes two public functions for pixel access:
+
+- `get_pixel`\
+  _Return the color `RGBA8` of a pixel at coordinates (x, y)_.\
+  **The caller must ensure the coordinates are within bounds**\
+  Parameters:
+  - `frame: &[u8]` - image buffer encoded in `RGBA8`
+  - `width: usize` - image width in pixels
+  - `x, y: usize` - pixel coordinates
+- `put_pixel`\
+  _Set the color of a pixel at coordinates (x, y)_.\
+  **The caller must ensure the coordinates are within bounds**\
+  Parameters:
+  - `frame: &mut [u8]` - mutable image buffer encoded in `RGBA8`
+  - `width: usize` - image width in pixels
+  - `x, y: usize` - pixel coordinates
+  - `color: rgb::RGBA8` - new pixel color
+
 `WinitHandler` creates a window for you and manages events and timing. You can package your code into a `chinchilib::GfxApp` implementing struct such as `MovingPixel` in the example bellow.
 
 `WinitHandler` will make calls to:

examples/moving_pixel.rs

@@ -39,7 +39,11 @@ const RED: rgb::RGBA8 = rgb::RGBA8 {
 };
 
 impl GfxApp for MovingPixel {
-    fn on_tick(&mut self, pressed_keys: &std::collections::HashSet<Key>) -> bool {
+    fn on_tick(
+        &mut self,
+        pressed_keys: &std::collections::HashSet<Key>,
+        window_size: (usize, usize),
+    ) -> bool {
         let mut needs_redraw = true;
         for key in pressed_keys {
             match key {

src/lib.rs

@@ -205,6 +205,12 @@ impl winit::application::ApplicationHandler for WinitHandler {
     }
 }
 
+pub fn get_pixel(frame: &[u8], width: usize, x: usize, y: usize) -> rgb::RGBA8 {
+    use rgb::*;
+    let idx = y * width + x;
+    frame.as_rgba()[idx]
+}
+
 pub fn put_pixel(frame: &mut [u8], width: usize, x: usize, y: usize, color: rgb::RGBA8) {
     use rgb::*;
     let idx = width * y + x;
@@ -278,7 +284,9 @@ impl WinFbx {
 
     fn on_tick(&mut self) {
         if self.app.done() == DoneStatus::NotDone {
-            self.needs_render = self.app.on_tick(&self.pressed_keys);
+            self.needs_render = self
+                .app
+                .on_tick(&self.pressed_keys, (self.width, self.height));
         }
         self.pressed_keys
             .retain(|candidate| !self.released_keys.contains(candidate));
@@ -333,7 +341,11 @@ pub enum DoneStatus {
 
 pub trait GfxApp {
     /// Every tick, this method gets called with currently pressed keys. Released keys during the tick are considered still pressed. But will be removed after this call.
-    fn on_tick(&mut self, pressed_keys: &std::collections::HashSet<Key>) -> bool;
+    fn on_tick(
+        &mut self,
+        pressed_keys: &std::collections::HashSet<Key>,
+        window_size: (usize, usize),
+    ) -> bool;
 
     /// You get the pixel array, so you can draw on it before the render.
     fn draw(&mut self, pixels: &mut Pixels, width: usize);