Implement gradient borders

1 files changed, 143 insertions, 0 deletions

diff --git a/src/render_helpers/gradient.rs b/src/render_helpers/gradient.rs
new file mode 100644
index 00000000..1dbed05a
--- /dev/null
+++ b/src/render_helpers/gradient.rs
@@ -0,0 +1,143 @@
+use std::f32::consts::{self, FRAC_PI_2, PI};
+
+use smithay::backend::renderer::element::{Element, Id, Kind, RenderElement, UnderlyingStorage};
+use smithay::backend::renderer::gles::element::PixelShaderElement;
+use smithay::backend::renderer::gles::{GlesError, GlesFrame, GlesRenderer, Uniform};
+use smithay::backend::renderer::utils::CommitCounter;
+use smithay::utils::{Buffer, Logical, Physical, Rectangle, Scale, Transform};
+
+use super::primary_gpu_pixel_shader::PrimaryGpuPixelShaderRenderElement;
+use super::renderer::NiriRenderer;
+use super::shaders::Shaders;
+use crate::backend::tty::{TtyFrame, TtyRenderer, TtyRendererError};
+
+/// Renders a sub- or super-rect of an angled linear gradient like CSS linear-gradient(angle, a, b).
+#[derive(Debug)]
+pub struct GradientRenderElement(PrimaryGpuPixelShaderRenderElement);
+
+impl GradientRenderElement {
+    pub fn new(
+        renderer: &mut impl NiriRenderer,
+        scale: Scale<f64>,
+        area: Rectangle<i32, Logical>,
+        gradient_area: Rectangle<i32, Logical>,
+        color_from: [f32; 4],
+        color_to: [f32; 4],
+        mut angle: f32,
+    ) -> Option<Self> {
+        let shader = Shaders::get(renderer).gradient_border.clone()?;
+        let g_offset = (area.loc - gradient_area.loc).to_f64().to_physical(scale);
+
+        let g_size = gradient_area.size.to_f64().to_physical(scale);
+        let (w, h) = (g_size.w as f32, g_size.h as f32);
+        let g_area_angle = f32::atan2(h, w);
+        let g_area_diag = f32::hypot(h, w);
+
+        // Normalize the angle to [0°; 360°).
+        while angle < 0. {
+            angle += consts::TAU;
+        }
+        while angle >= consts::TAU {
+            angle -= consts::TAU;
+        }
+
+        let angle_diag_to_grad =
+            if (0. ..=FRAC_PI_2).contains(&angle) || (PI..=PI + FRAC_PI_2).contains(&angle) {
+                angle - g_area_angle
+            } else {
+                (PI - angle) - g_area_angle
+            };
+        let g_total = angle_diag_to_grad.cos().abs() * g_area_diag;
+
+        let elem = PixelShaderElement::new(
+            shader,
+            area,
+            None,
+            1.,
+            vec![
+                Uniform::new("color_from", color_from),
+                Uniform::new("color_to", color_to),
+                Uniform::new("angle", angle),
+                Uniform::new("gradient_offset", (g_offset.x as f32, g_offset.y as f32)),
+                Uniform::new("gradient_width", w),
+                Uniform::new("gradient_total", g_total),
+            ],
+            Kind::Unspecified,
+        );
+        Some(Self(PrimaryGpuPixelShaderRenderElement(elem)))
+    }
+}
+
+impl Element for GradientRenderElement {
+    fn id(&self) -> &Id {
+        self.0.id()
+    }
+
+    fn current_commit(&self) -> CommitCounter {
+        self.0.current_commit()
+    }
+
+    fn geometry(&self, scale: Scale<f64>) -> Rectangle<i32, Physical> {
+        self.0.geometry(scale)
+    }
+
+    fn transform(&self) -> Transform {
+        self.0.transform()
+    }
+
+    fn src(&self) -> Rectangle<f64, Buffer> {
+        self.0.src()
+    }
+
+    fn damage_since(
+        &self,
+        scale: Scale<f64>,
+        commit: Option<CommitCounter>,
+    ) -> Vec<Rectangle<i32, Physical>> {
+        self.0.damage_since(scale, commit)
+    }
+
+    fn opaque_regions(&self, scale: Scale<f64>) -> Vec<Rectangle<i32, Physical>> {
+        self.0.opaque_regions(scale)
+    }
+
+    fn alpha(&self) -> f32 {
+        self.0.alpha()
+    }
+
+    fn kind(&self) -> Kind {
+        self.0.kind()
+    }
+}
+
+impl RenderElement<GlesRenderer> for GradientRenderElement {
+    fn draw(
+        &self,
+        frame: &mut GlesFrame<'_>,
+        src: Rectangle<f64, Buffer>,
+        dst: Rectangle<i32, Physical>,
+        damage: &[Rectangle<i32, Physical>],
+    ) -> Result<(), GlesError> {
+        RenderElement::<GlesRenderer>::draw(&self.0, frame, src, dst, damage)
+    }
+
+    fn underlying_storage(&self, renderer: &mut GlesRenderer) -> Option<UnderlyingStorage> {
+        self.0.underlying_storage(renderer)
+    }
+}
+
+impl<'render> RenderElement<TtyRenderer<'render>> for GradientRenderElement {
+    fn draw(
+        &self,
+        frame: &mut TtyFrame<'_, '_>,
+        src: Rectangle<f64, Buffer>,
+        dst: Rectangle<i32, Physical>,
+        damage: &[Rectangle<i32, Physical>],
+    ) -> Result<(), TtyRendererError<'render>> {
+        RenderElement::<TtyRenderer<'_>>::draw(&self.0, frame, src, dst, damage)
+    }
+
+    fn underlying_storage(&self, renderer: &mut TtyRenderer<'render>) -> Option<UnderlyingStorage> {
+        self.0.underlying_storage(renderer)
+    }
+}