Add Custom Shader Uniforms for Cursor Effects

src/renderer/OpenGL.zig

@@ -1951,6 +1951,13 @@ fn addCursor(
         .glyph_offset_y = render.glyph.offset_y,
     });
 
+    // Update cursor uniforms only when custom shaders are loaded
+    if (self.gl_state) |*gl_state| {
+        if (gl_state.custom) |*custom_state| {
+            custom_state.addCursor(self.size, screen.cursor, cursor_style, render.glyph);
+        }
+    }
+
     return &self.cells.items[self.cells.items.len - 1];
 }
 

src/renderer/opengl/custom.zig

@@ -1,6 +1,9 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
+const CursorStyle = @import("../../renderer/cursor.zig").Style;
 const gl = @import("opengl");
+const Glyph = @import("../../font/Glyph.zig");
+const Screen = @import("../../terminal/Screen.zig");
 const Size = @import("../size.zig").Size;
 
 const log = std.log.scoped(.opengl_custom);
@@ -22,6 +25,9 @@ pub const Uniforms = extern struct {
     mouse: [4]f32 align(16) = .{ 0, 0, 0, 0 },
     date: [4]f32 align(16) = .{ 0, 0, 0, 0 },
     sample_rate: f32 align(4) = 1,
+    current_cursor: [4]f32 align(16) = .{ 0, 0, 0, 0 }, 
+    previous_cursor: [4]f32 align(16) = .{ 0, 0, 0, 0 }, 
+    cursor_change_time: f32 align(4) = 1 
 };
 
 /// The state associated with custom shaders. This should only be initialized
@@ -176,6 +182,37 @@ pub const State = struct {
             null,
         );
     }
+
+    // Update the cursor related uniforms
+    pub fn addCursor(self: *State, size: Size, cursor: Screen.Cursor, cursor_style: CursorStyle, glyph: Glyph) void {
+        // Converts the cursor's cell-based position to pixel coordinates.
+        // Additionally, the y-position is adjusted to account for the inverted Y-axis
+        // in the window coordinate system used by gl_FragCoord, where the origin is at the bottom-left.
+        // The offset from the glyph is also added to position the cursor correctly.
+        const current_x: f32 = @as(f32, @floatFromInt(cursor.x * size.cell.width + size.padding.left)) + @as(f32, @floatFromInt(glyph.offset_x));
+        const current_y: f32 = @as(f32, @floatFromInt(size.screen.height - size.padding.top - (cursor.y + 1) * size.cell.height)) + @as(f32, @floatFromInt(glyph.offset_y));
+
+        // Determine the cursor's width and height based on the cursor style:
+        // - A bar-style cursor has a width of 1.0, while other cursor styles use the glyph's width.
+        const cursor_width: f32 = if (cursor_style == .bar) 1.0 else @floatFromInt(glyph.width);
+        const cursor_height: f32 = @floatFromInt(glyph.height);
+
+        // Check if the cursor's position or size has changed compared to the previously set values.
+        const cursor_changed: bool = current_x != self.uniforms.current_cursor[0] or
+            current_y != self.uniforms.current_cursor[1] or
+            cursor_width != self.uniforms.current_cursor[2] or
+            cursor_height != self.uniforms.current_cursor[3];
+
+        if (cursor_changed) {
+            self.uniforms.previous_cursor = self.uniforms.current_cursor;
+            self.uniforms.current_cursor = .{ current_x, current_y, cursor_width, cursor_height };
+
+            // Calculate the time elapsed since the first frame to update the cursor change time.
+            const now = std.time.Instant.now() catch self.last_frame_time;
+            const since_ns: f32 = @floatFromInt(now.since(self.first_frame_time));
+            self.uniforms.cursor_change_time = since_ns / std.time.ns_per_s;
+        }
+    }
 
     /// Call this prior to drawing a frame to update the time
     /// and synchronize the uniforms. This synchronizes uniforms

src/renderer/shaders/shadertoy_prefix.glsl

@@ -11,6 +11,9 @@ layout(binding = 0) uniform Globals {
     uniform vec4	iMouse;
     uniform vec4	iDate;
     uniform float	iSampleRate;
+    uniform vec4	iCurrentCursor;
+    uniform vec4	iPreviousCursor;
+    uniform float	iTimeCursorChange;
 };
 
 layout(binding = 0) uniform sampler2D	iChannel0;