Draw updates to an intermediate bitmap context under macOS

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

@@ -31,12 +31,14 @@ use cocoa::foundation::{
  NSArray, NSAutoreleasePool, NSInteger, NSPoint, NSRect, NSSize, NSString, NSUInteger,
 };
 use core_graphics::context::CGContextRef;
+use core_graphics::sys::CGContext;
 use foreign_types::ForeignTypeRef;
 use lazy_static::lazy_static;
 use objc::declare::ClassDecl;
 use objc::rc::WeakPtr;
 use objc::runtime::{Class, Object, Protocol, Sel};
 use objc::{class, msg_send, sel, sel_impl};
+use piet_common::InterpolationMode;
 use tracing::{debug, error, info};
 
 #[cfg(feature = "raw-win-handle")]
@@ -850,27 +852,59 @@ extern "C" fn view_will_draw(this: &mut Object, _: Sel) {
 
 extern "C" fn draw_rect(this: &mut Object, _: Sel, dirtyRect: NSRect) {
  unsafe {
- let context: id = msg_send![class![NSGraphicsContext], currentContext];
- //FIXME: when core_graphics is at 0.20, we should be able to use
- //core_graphics::sys::CGContextRef as our pointer type.
- let cgcontext_ptr: *mut <CGContextRef as ForeignTypeRef>::CType =
-  msg_send![context, CGContext];
- let cgcontext_ref = CGContextRef::from_ptr_mut(cgcontext_ptr);
+ let cgcontext_id: id = msg_send![class![NSGraphicsContext], currentContext];
+ let cgcontext_ptr: &mut CGContext = msg_send![cgcontext_id, CGContext];
+ let cgcontext_ref: &mut CGContextRef = CGContextRef::from_ptr_mut(cgcontext_ptr);
+
+ let view_state: *mut c_void = *this.get_ivar("viewState");
+ let view_state: &mut ViewState = &mut *(view_state as *mut ViewState);
 
  // FIXME: use the actual invalid region instead of just this bounding box.
  // https://developer.apple.com/documentation/appkit/nsview/1483772-getrectsbeingdrawn?language=objc
- let rect = Rect::from_origin_size(
+ let invalid_region_rect = Rect::from_origin_size(
  (dirtyRect.origin.x, dirtyRect.origin.y),
  (dirtyRect.size.width, dirtyRect.size.height),
  );
- let invalid = Region::from(rect);
+ let invalid_region = Region::from(invalid_region_rect);
 
- let view_state: *mut c_void = *this.get_ivar("viewState");
- let view_state = &mut *(view_state as *mut ViewState);
- let mut piet_ctx = Piet::new_y_down(cgcontext_ref, Some(view_state.text.clone()));
+ let context_size = NSView::frame(this as *mut _);
+ let context_width = context_size.size.width;
+ let context_height = context_size.size.height;
+
+ let mut cache_ctx = core_graphics::context::CGContext::create_bitmap_context(
+ None,
+ context_width as usize,
+ context_height as usize,
+ 8,
+ 0,
+ &core_graphics::color_space::CGColorSpace::create_device_rgb(),
+ core_graphics::base::kCGImageAlphaPremultipliedLast,
+ );
+
+ let mut piet_bitmap_ctx = Piet::new_y_up(
+ &mut cache_ctx,
+ context_height as f64,
+ Some(view_state.text.clone()),
+ );
+
+ (*view_state)
+ .handler
+ .paint(&mut piet_bitmap_ctx, &invalid_region);
+
+ let cache_capture = piet_bitmap_ctx
+ .capture_image_area(invalid_region_rect)
+ .expect("Failed to retrieve content from render cache context");
+ let unwrapped_cache = cache_capture.as_cgimage().expect("Cropped image was empty");
+ let rewrapped_cache = piet_common::CoreGraphicsImage::YDown(unwrapped_cache.clone());
+
+ let mut window_ctx = Piet::new_y_down(cgcontext_ref, Some(view_state.text.clone()));
+ window_ctx.draw_image(
+ &rewrapped_cache,
+ invalid_region_rect,
+ InterpolationMode::Bilinear,
+ );
 
- (*view_state).handler.paint(&mut piet_ctx, &invalid);
- if let Err(e) = piet_ctx.finish() {
+ if let Err(e) = window_ctx.finish() {
  error!("{}", e)
  }