clear color buffer on vid refresh

ferretro_components/src/base/mod.rs

@@ -210,6 +210,12 @@ impl RetroCallbacks for RetroComponentBase {
         }
     }
 
+    fn video_refresh_hw(&mut self, width: c_uint, height: c_uint) {
+        for comp in &mut self.components {
+            comp.video_refresh_hw(width, height);
+        }
+    }
+
     fn audio_sample(&mut self, left: i16, right: i16) {
         for comp in &mut self.components {
             comp.audio_sample(left, right);

ferretro_components/src/provided/sdl2/opengl.rs

@@ -4,9 +4,14 @@ use crate::prelude::*;
 use std::ffi::CStr;
 use std::os::raw::c_uint;
 
-use sdl2::{Sdl, VideoSubsystem};
+use sdl2::Sdl;
 use sdl2::video::{GLContext, Window};
 
+// TODO: get these from somewhere better without pulling in too much of a mess for the sdl2 feature
+const GL_FRAMEBUFFER_BINDING: c_uint = 0x8CA6;
+const GL_COLOR_BUFFER_BIT: c_uint = 0x00004000;
+
+#[allow(non_snake_case)]
 pub struct SimpleSdl2OpenglComponent {
     window: Window,
     window_fbo: c_uint,
@@ -14,6 +19,8 @@ pub struct SimpleSdl2OpenglComponent {
     pixel_format: sdl2::pixels::PixelFormatEnum,
     hw_context_reset_fn: Option<HwContextResetFn>,
     hw_context_destroy_fn: Option<HwContextResetFn>,
+    glGetIntegerv: unsafe extern "C" fn(c_uint, *mut c_uint),
+    glClear: unsafe extern "C" fn(c_uint),
 }
 
 impl SimpleSdl2OpenglComponent {
@@ -33,10 +40,19 @@ impl SimpleSdl2OpenglComponent {
             .opengl()
             .build()?;
 
+        #[allow(non_snake_case)]
+        let glGetIntegerv: unsafe extern "C" fn(c_uint, *mut c_uint) = unsafe {
+            std::mem::transmute(video.gl_get_proc_address("glGetIntegerv"))
+        };
+        #[allow(non_snake_case)]
+        let glClear: unsafe extern "C" fn(c_uint) = unsafe {
+            std::mem::transmute(video.gl_get_proc_address("glClear"))
+        };
+
         // http://forums.libsdl.org/viewtopic.php?p=43353
         // likely to remain `0` on any platform that isn't iOS, but we'll do it anyhow
         let gl_context = window.gl_create_context()?;
-        let window_fbo = Self::current_framebuffer_binding(&video);
+        let window_fbo = unsafe { let mut fbo =  0; glGetIntegerv(GL_FRAMEBUFFER_BINDING, &mut fbo); fbo };
 
         Ok(SimpleSdl2OpenglComponent {
             window,
@@ -45,18 +61,16 @@ impl SimpleSdl2OpenglComponent {
             pixel_format,
             hw_context_reset_fn: None,
             hw_context_destroy_fn: None,
+            glGetIntegerv,
+            glClear,
         })
     }
 
-    fn current_framebuffer_binding(video: &VideoSubsystem) -> c_uint {
+    fn current_framebuffer_binding(&self) -> c_uint {
         let mut fbo: c_uint = 0;
         unsafe {
-            const GL_FRAMEBUFFER_BINDING: c_uint = 0x8CA6;
             #[allow(non_snake_case)]
-                let glGetIntegerv: unsafe extern "C" fn(c_uint, *mut c_uint) = std::mem::transmute(
+            (self.glGetIntegerv)(GL_FRAMEBUFFER_BINDING, &mut fbo);
-                video.gl_get_proc_address("glGetIntegerv")
-            );
-            glGetIntegerv(GL_FRAMEBUFFER_BINDING, &mut fbo);
         }
         eprintln!("get_framebuffer_binding: {}", fbo);
         fbo
@@ -72,6 +86,10 @@ impl SimpleSdl2OpenglComponent {
 }
 
 impl RetroCallbacks for SimpleSdl2OpenglComponent {
+    fn video_refresh_hw(&mut self, _width: c_uint, _height: c_uint) {
+        unsafe { (self.glClear)(GL_COLOR_BUFFER_BIT); }
+    }
+
     fn set_pixel_format(&mut self, pix_fmt: PixelFormat) -> Option<bool> {
         self.pixel_format = match pix_fmt {
             PixelFormat::ARGB1555 => sdl2::pixels::PixelFormatEnum::RGB555,
@@ -106,7 +124,7 @@ impl RetroCallbacks for SimpleSdl2OpenglComponent {
         self.window.set_size(geom.base_width, geom.base_height).ok()?;
         self.call_context_destroy()?;
         self.gl_context = self.window.gl_create_context().ok()?;
-        self.window_fbo = Self::current_framebuffer_binding(self.window.subsystem());
+        self.window_fbo = self.current_framebuffer_binding();
         self.call_context_reset()?;
         Some(true)
     }