From 47f10dffd99c3eb352ebea1834a833bde29a2656 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Ram=C3=B3n=20Jim=C3=A9nez?=
 <hector0193@gmail.com>
Date: Mon, 18 May 2020 20:46:09 +0200
Subject: [PATCH] Implement clipping support

---
 examples/clipping.rs | 112 +++++++++++++++++++++++++++++++++++++++++++
 src/pipeline.rs      |  11 +++++
 2 files changed, 123 insertions(+)
 create mode 100644 examples/clipping.rs

diff --git a/examples/clipping.rs b/examples/clipping.rs
new file mode 100644
index 0000000..1afee93
--- /dev/null
+++ b/examples/clipping.rs
@@ -0,0 +1,112 @@
+use glow::HasContext;
+use glow_glyph::{GlyphBrushBuilder, Region, Scale, Section};
+
+fn main() -> Result<(), String> {
+    env_logger::init();
+
+    // Open window and create a surface
+    let event_loop = glutin::event_loop::EventLoop::new();
+
+    let window_builder =
+        glutin::window::WindowBuilder::new().with_resizable(false);
+
+    let context = glutin::ContextBuilder::new()
+        .with_srgb(true)
+        .build_windowed(window_builder, &event_loop)
+        .expect("Open window");
+
+    let context =
+        unsafe { context.make_current().expect("Make OpenGL context current") };
+
+    let mut size = context.window().inner_size();
+
+    // Initialize OpenGL
+    let gl = glow::Context::from_loader_function(|s| {
+        context.get_proc_address(s) as *const _
+    });
+
+    // Prepare glyph_brush
+    let inconsolata: &[u8] = include_bytes!("Inconsolata-Regular.ttf");
+    let mut glyph_brush = GlyphBrushBuilder::using_font_bytes(inconsolata)
+        .expect("Load fonts")
+        .build(&gl);
+
+    // Render loop
+    context.window().request_redraw();
+
+    unsafe {
+        // Enable auto-conversion from/to sRGB
+        gl.enable(glow::FRAMEBUFFER_SRGB);
+
+        // Enable alpha blending
+        gl.enable(glow::BLEND);
+        gl.blend_func(glow::SRC_ALPHA, glow::ONE_MINUS_SRC_ALPHA);
+
+        gl.clear_color(0.4, 0.4, 0.4, 1.0);
+    }
+
+    event_loop.run(move |event, _, control_flow| match event {
+        glutin::event::Event::WindowEvent {
+            event: glutin::event::WindowEvent::CloseRequested,
+            ..
+        } => *control_flow = glutin::event_loop::ControlFlow::Exit,
+        glutin::event::Event::WindowEvent {
+            event: glutin::event::WindowEvent::Resized(new_size),
+            ..
+        } => {
+            context.resize(new_size);
+
+            unsafe {
+                gl.viewport(0, 0, new_size.width as _, new_size.height as _);
+            }
+
+            size = new_size;
+        }
+        glutin::event::Event::RedrawRequested { .. } => {
+            unsafe { gl.clear(glow::COLOR_BUFFER_BIT) }
+
+            glyph_brush.queue(Section {
+                text: "Hello glow_glyph!",
+                screen_position: (30.0, 30.0),
+                color: [0.0, 0.0, 0.0, 1.0],
+                scale: Scale { x: 40.0, y: 40.0 },
+                bounds: (size.width as f32, size.height as f32),
+                ..Section::default()
+            });
+
+            glyph_brush
+                .draw_queued(&gl, size.width, size.height)
+                .expect("Draw queued");
+
+            glyph_brush.queue(Section {
+                text: "Hello glow_glyph!",
+                screen_position: (30.0, 90.0),
+                color: [1.0, 1.0, 1.0, 1.0],
+                scale: Scale { x: 40.0, y: 40.0 },
+                bounds: (size.width as f32, size.height as f32),
+                ..Section::default()
+            });
+
+            glyph_brush
+                .draw_queued_with_transform_and_scissoring(
+                    &gl,
+                    glow_glyph::orthographic_projection(
+                        size.width,
+                        size.height,
+                    ),
+                    Region {
+                        x: 40,
+                        y: size.height - 120,
+                        width: 200,
+                        height: 15,
+                    },
+                )
+                .expect("Draw queued");
+
+            context.swap_buffers().expect("Swap buffers");
+        }
+        _ => {
+            *control_flow = glutin::event_loop::ControlFlow::Wait;
+        }
+    })
+}
diff --git a/src/pipeline.rs b/src/pipeline.rs
index c5b9b38..31cda1e 100644
--- a/src/pipeline.rs
+++ b/src/pipeline.rs
@@ -75,6 +75,16 @@ impl Pipeline {
         }
 
         unsafe {
+            if let Some(region) = region {
+                gl.enable(glow::SCISSOR_TEST);
+                gl.scissor(
+                    region.x as i32,
+                    region.y as i32,
+                    region.width as i32,
+                    region.height as i32,
+                );
+            }
+
             gl.active_texture(glow::TEXTURE0);
             gl.bind_texture(glow::TEXTURE_2D, Some(self.cache.texture));
             gl.uniform_1_i32(Some(1), 0);
@@ -90,6 +100,7 @@ impl Pipeline {
 
             gl.bind_vertex_array(None);
             gl.bind_texture(glow::TEXTURE_2D, None);
+            gl.disable(glow::SCISSOR_TEST);
             gl.use_program(None);
         }
     }