when losing focus, show hollow box

shaders/cell.f.glsl

@@ -7,12 +7,23 @@ flat in uint mode;
 // background color. Otherwise, this is the foreground color.
 flat in vec4 color;
 
+// The position of the cells top-left corner.
+flat in vec2 screen_cell_pos;
+
+// Position the fragment coordinate to the upper left
+layout(origin_upper_left) in vec4 gl_FragCoord;
+
 // Font texture
 uniform sampler2D text;
 
+// Dimensions of the cell
+uniform vec2 cell_size;
+
 // See fragment shader
 const uint MODE_BG = 1u;
 const uint MODE_FG = 2u;
+const uint MODE_CURSOR_RECT = 3u;
+const uint MODE_CURSOR_RECT_HOLLOW = 4u;
 
 void main() {
     switch (mode) {
@@ -24,5 +35,45 @@ void main() {
         float a = texture(text, glyph_tex_coords).r;
         gl_FragColor = vec4(color.rgb, color.a*a);
         break;
+
+    case MODE_CURSOR_RECT:
+        gl_FragColor = color;
+        break;
+
+    case MODE_CURSOR_RECT_HOLLOW:
+        // Okay so yeah this is probably horrendously slow and a shader
+        // should never do this, but we only ever render a cursor for ONE
+        // rectangle so we take the slowdown for that one.
+
+        // Default to no color.
+        gl_FragColor = vec4(0., 0., 0, 0.0);
+
+        // We subtracted one from cell size because our coordinates start at 0.
+        // So a width of 50 means max pixel of 49.
+        vec2 cell_size_coords = cell_size - 1;
+
+        // Apply padding
+        vec2 padding = vec2(1.,1.);
+        cell_size_coords = cell_size_coords - (padding * 2);
+        vec2 screen_cell_pos_padded = screen_cell_pos + padding;
+
+        // Convert our frag coord to offset of this cell. We have to subtract
+        // 0.5 because the frag coord is in center pixels.
+        vec2 cell_frag_coord = gl_FragCoord.xy - screen_cell_pos_padded - 0.5;
+
+        // If the frag coords are in the bounds, then we color it.
+        const float eps = 0.1;
+        if (cell_frag_coord.x >= 0 && cell_frag_coord.y >= 0 &&
+                cell_frag_coord.x <= cell_size_coords.x &&
+                cell_frag_coord.y <= cell_size_coords.y) {
+            if (abs(cell_frag_coord.x) < eps ||
+                    abs(cell_frag_coord.x - cell_size_coords.x) < eps ||
+                    abs(cell_frag_coord.y) < eps ||
+                    abs(cell_frag_coord.y - cell_size_coords.y) < eps) {
+                gl_FragColor = color;
+            }
+        }
+
+        break;
     }
 }

shaders/cell.v.glsl

@@ -6,6 +6,8 @@
 // NOTE: this must be kept in sync with the fragment shader
 const uint MODE_BG = 1u;
 const uint MODE_FG = 2u;
+const uint MODE_CURSOR_RECT = 3u;
+const uint MODE_CURSOR_RECT_HOLLOW = 4u;
 
 // The grid coordinates (x, y) where x < columns and y < rows
 layout (location = 0) in vec2 grid_coord;
@@ -38,6 +40,10 @@ flat out vec4 color;
 // The x/y coordinate for the glyph representing the font.
 out vec2 glyph_tex_coords;
 
+// The position of the cell top-left corner in screen cords. z and w
+// are width and height.
+flat out vec2 screen_cell_pos;
+
 // Pass the mode forward to the fragment shader.
 flat out uint mode;
 
@@ -121,5 +127,24 @@ void main() {
         // Set our foreground color output
         color = fg_color_in / 255.;
         break;
+
+    case MODE_CURSOR_RECT:
+        // Same as background since we're taking up the whole cell.
+        cell_pos = cell_pos + cell_size * position;
+
+        gl_Position = projection * vec4(cell_pos, 0.0, 1.0);
+        color = bg_color_in / 255.0;
+        break;
+
+    case MODE_CURSOR_RECT_HOLLOW:
+        // Top-left position of this cell is needed for the hollow rect.
+        screen_cell_pos = cell_pos;
+
+        // Same as background since we're taking up the whole cell.
+        cell_pos = cell_pos + cell_size * position;
+
+        gl_Position = projection * vec4(cell_pos, 0.0, 1.0);
+        color = bg_color_in / 255.0;
+        break;
     }
 }

src/Grid.zig

@@ -37,6 +37,12 @@ font_atlas: FontAtlas,
 /// Whether the cursor is visible or not. This is used to control cursor
 /// blinking.
 cursor_visible: bool,
+cursor_style: CursorStyle,
+
+const CursorStyle = enum(u8) {
+    box = 3,
+    box_hollow = 4,
+};
 
 /// The raw structure that maps directly to the buffer sent to the vertex shader.
 const GPUCell = struct {
@@ -211,6 +217,7 @@ pub fn init(alloc: Allocator) !Grid {
         .texture = tex,
         .font_atlas = font,
         .cursor_visible = true,
+        .cursor_style = .box,
     };
 }
 
@@ -295,7 +302,7 @@ pub fn updateCells(self: *Grid, term: Terminal) !void {
     // Draw the cursor
     if (self.cursor_visible) {
         self.cells.appendAssumeCapacity(.{
-            .mode = 1,
+            .mode = @enumToInt(self.cursor_style),
             .grid_col = @intCast(u16, term.cursor.x),
             .grid_row = @intCast(u16, term.cursor.y),
             .fg_r = 0,

src/Window.zig

@@ -221,10 +221,13 @@ fn keyCallback(
 fn focusCallback(window: glfw.Window, focused: bool) void {
     const win = window.getUserPointer(Window) orelse return;
     if (focused) {
-        win.cursor_timer.start(cursorTimerCallback, 800, 800) catch unreachable;
         win.wakeup = true;
-    } else {
+        win.cursor_timer.start(cursorTimerCallback, 0, 800) catch unreachable;
+        win.grid.cursor_style = .box;
         win.grid.cursor_visible = false;
+    } else {
+        win.grid.cursor_visible = true;
+        win.grid.cursor_style = .box_hollow;
         win.grid.updateCells(win.terminal) catch unreachable;
         win.cursor_timer.stop() catch unreachable;
     }