glow on web: simplify the webgl2 vs webgl1 selection

egui_web/src/glow_wrapping.rs

@@ -86,27 +86,36 @@ impl crate::Painter for WrappedGlowPainter {
 }
 
 /// Returns glow context and shader prefix.
-fn init_glow_context_from_canvas(canvas: &HtmlCanvasElement) -> (glow::Context, &str) {
-    let gl2_ctx = canvas
-        .get_context("webgl2")
-        .expect("Failed to query about WebGL2 context");
+fn init_glow_context_from_canvas(canvas: &HtmlCanvasElement) -> (glow::Context, &'static str) {
+    const BEST_FIRST: bool = true;
 
-    if let Some(gl2_ctx) = gl2_ctx {
-        crate::console_log("WebGL2 found.");
-        let gl2_ctx = gl2_ctx
-            .dyn_into::<web_sys::WebGl2RenderingContext>()
-            .unwrap();
-        let glow_ctx = glow::Context::from_webgl2_context(gl2_ctx);
-        let shader_prefix = "";
-        (glow_ctx, shader_prefix)
+    let result = if BEST_FIRST {
+        // Trying WebGl2 first
+        init_webgl2(canvas).or_else(|| init_webgl1(canvas))
     } else {
-        let gl1 = canvas
+        // Trying WebGl1 first (useful for testing).
+        crate::console_warn("Looking for WebGL1 first");
+        init_webgl1(canvas).or_else(|| init_webgl2(canvas))
+    };
+
+    if let Some(result) = result {
+        result
+    } else {
+        panic!("WebGL isn't supported");
+    }
+}
+
+fn init_webgl1(canvas: &HtmlCanvasElement) -> Option<(glow::Context, &'static str)> {
+    let gl1_ctx = canvas
         .get_context("webgl")
-            .expect("Failed to query about WebGL1 context");
+        .expect("Failed to query about WebGL2 context");
 
-        if let Some(gl1) = gl1 {
-            crate::console_log("WebGL2 not available - falling back to WebGL1.");
-            let gl1_ctx = gl1.dyn_into::<web_sys::WebGlRenderingContext>().unwrap();
+    let gl1_ctx = gl1_ctx?;
+    crate::console_log("WebGL1 selected.");
+
+    let gl1_ctx = gl1_ctx
+        .dyn_into::<web_sys::WebGlRenderingContext>()
+        .unwrap();
 
     let shader_prefix = if crate::webgl1_requires_brightening(&gl1_ctx) {
         crate::console_log("Enabling webkitGTK brightening workaround.");
@@ -117,11 +126,24 @@ fn init_glow_context_from_canvas(canvas: &HtmlCanvasElement) -> (glow::Context,
 
     let glow_ctx = glow::Context::from_webgl1_context(gl1_ctx);
 
-            (glow_ctx, shader_prefix)
-        } else {
-            panic!("Failed to get WebGL context.");
-        }
-    }
+    Some((glow_ctx, shader_prefix))
+}
+
+fn init_webgl2(canvas: &HtmlCanvasElement) -> Option<(glow::Context, &'static str)> {
+    let gl2_ctx = canvas
+        .get_context("webgl2")
+        .expect("Failed to query about WebGL2 context");
+
+    let gl2_ctx = gl2_ctx?;
+    crate::console_log("WebGL2 selected.");
+
+    let gl2_ctx = gl2_ctx
+        .dyn_into::<web_sys::WebGl2RenderingContext>()
+        .unwrap();
+    let glow_ctx = glow::Context::from_webgl2_context(gl2_ctx);
+    let shader_prefix = "";
+
+    Some((glow_ctx, shader_prefix))
 }
 
 trait DummyWebGLConstructor {
@@ -133,10 +155,10 @@ trait DummyWebGLConstructor {
 #[cfg(not(target_arch = "wasm32"))]
 impl DummyWebGLConstructor for glow::Context {
     fn from_webgl1_context(_context: WebGlRenderingContext) -> Self {
-        panic!("you cant use egui_web(glow) on native")
+        panic!("you can't use egui_web(glow) on native")
     }
 
     fn from_webgl2_context(_context: WebGl2RenderingContext) -> Self {
-        panic!("you cant use egui_web(glow) on native")
+        panic!("you can't use egui_web(glow) on native")
     }
 }