Fix cursor rendering when on first cell of multicell

kitty/cell_vertex.glsl

@@ -9,7 +9,8 @@ layout(std140) uniform CellRenderData {
     uint default_fg, highlight_fg, highlight_bg, cursor_fg, cursor_bg, url_color, url_style, inverted;
 
     uint xnum, ynum, sprites_xnum, sprites_ynum, cursor_fg_sprite_idx, cell_height;
-    float cursor_x, cursor_y, cursor_w, cursor_opacity;
+    uint cursor_x1, cursor_x2, cursor_y1, cursor_y2;
+    float cursor_opacity;
 
     // must have unique entries with 0 being default_bg and unset being UINT32_MAX
     uint bg_colors0, bg_colors1, bg_colors2, bg_colors3, bg_colors4, bg_colors5, bg_colors6, bg_colors7;
@@ -81,6 +82,11 @@ float one_if_equal_zero_otherwise(int a, int b) {
     return 1.0f - clamp(abs(float(a) - float(b)), 0.0f, 1.0f);
 }
 
+float one_if_equal_zero_otherwise(uint a, uint b) {
+    return 1.0f - clamp(abs(float(a) - float(b)), 0.0f, 1.0f);
+}
+
+
 uint resolve_color(uint c, uint defval) {
     // Convert a cell color to an actual color based on the color table
     int t = int(c & BYTE_MASK);
@@ -144,18 +150,10 @@ vec3 choose_color(float q, vec3 a, vec3 b) {
     return mix(b, a, q);
 }
 
-float are_integers_equal(float a, float b) { // return 1 if equal otherwise 0
+float is_cursor(uint x, uint y) {
-    float delta = abs(a - b);  // delta can be 0, 1 or larger
+    uint clamped_x = clamp(x, cursor_x1, cursor_x2);
-    return step(delta, 0.5); // 0 if 0.5 < delta else 1
+    uint clamped_y = clamp(y, cursor_y1, cursor_y2);
-}
+    return one_if_equal_zero_otherwise(x, clamped_x) * one_if_equal_zero_otherwise(y, clamped_y);
-
-float is_cursor(uint xi, uint y) {
-    float x = float(xi);
-    float y_equal = are_integers_equal(float(y), cursor_y);
-    float x1_equal = are_integers_equal(x, cursor_x);
-    float x2_equal = are_integers_equal(x, cursor_w);
-    float x_equal = step(0.5, x1_equal + x2_equal);
-    return step(2.0, x_equal + y_equal);
 }
 // }}}
 

kitty/line.h

@@ -13,7 +13,6 @@
 // TODO: Test handling of calt ligatures with scale see is_group_calt_ligature()
 // TODO: Handle selection with multicell
 // TODO: URL detection with multicell
-// TODO: Cursor rendering over multicell
 // TODO: Wrapping of multicell draw commands
 // TODO: Handle rewrap and restitch of multiline chars
 // TODO: Handle rewrap when a character is too wide/tall to fit on resized screen

kitty/shaders.c

@@ -369,7 +369,9 @@ cell_update_uniform_block(ssize_t vao_idx, Screen *screen, int uniform_buffer, c
         GLuint default_fg, highlight_fg, highlight_bg, cursor_fg, cursor_bg, url_color, url_style, inverted;
 
         GLuint xnum, ynum, sprites_xnum, sprites_ynum, cursor_fg_sprite_idx, cell_height;
-        GLfloat cursor_x, cursor_y, cursor_w, cursor_opacity;
+        GLuint cursor_x1, cursor_x2, cursor_y1, cursor_y2;
+        GLfloat cursor_opacity;
+
         GLuint bg_colors0, bg_colors1, bg_colors2, bg_colors3, bg_colors4, bg_colors5, bg_colors6, bg_colors7;
         GLfloat bg_opacities0, bg_opacities1, bg_opacities2, bg_opacities3, bg_opacities4, bg_opacities5, bg_opacities6, bg_opacities7;
     };
@@ -402,7 +404,8 @@ cell_update_uniform_block(ssize_t vao_idx, Screen *screen, int uniform_buffer, c
     enum { BLOCK_IDX = 0, BEAM_IDX = 2, UNDERLINE_IDX = 3, UNFOCUSED_IDX = 4 };
     Line *line_for_cursor = NULL;
     if (cursor->opacity > 0) {
-        rd->cursor_x = cursor->x, rd->cursor_y = cursor->y;
+        rd->cursor_x1 = cursor->x, rd->cursor_y1 = cursor->y;
+        rd->cursor_x2 = cursor->x, rd->cursor_y2 = cursor->y;
         rd->cursor_opacity = cursor->opacity;
         CursorShape cs = (cursor->is_focused || OPT(cursor_shape_unfocused) == NO_CURSOR_SHAPE) ? cursor->shape : OPT(cursor_shape_unfocused);
         switch(cs) {
@@ -427,6 +430,24 @@ cell_update_uniform_block(ssize_t vao_idx, Screen *screen, int uniform_buffer, c
         }
         if (line_for_cursor) {
             colors_for_cell(line_for_cursor, cp, &cell_color_x, &cell_fg, &cell_bg, &reversed);
+            const CPUCell *cursor_cell;
+            const bool large_cursor = ((cursor_cell = &line_for_cursor->cpu_cells[cursor->x])->is_multicell) && cursor_cell->x == 0 && cursor_cell->y == 0;
+            if (large_cursor) {
+                switch(cs) {
+                    case CURSOR_BEAM:
+                        rd->cursor_y2 += cursor_cell->scale - 1; break;
+                    case CURSOR_UNDERLINE:
+                        rd->cursor_y1 += cursor_cell->scale - 1;
+                        rd->cursor_y2 = rd->cursor_y1;
+                        rd->cursor_x2 += mcd_x_limit(cursor_cell) - 1;
+                        break;
+                    case CURSOR_BLOCK:
+                        rd->cursor_y2 += cursor_cell->scale - 1;
+                        rd->cursor_x2 += mcd_x_limit(cursor_cell) - 1;
+                        break;
+                    case CURSOR_HOLLOW: case NUM_OF_CURSOR_SHAPES: case NO_CURSOR_SHAPE: break;
+                };
+            }
         }
         if (IS_SPECIAL_COLOR(cursor_color)) {
             if (line_for_cursor) pick_cursor_color(line_for_cursor, cp, cell_fg, cell_bg, cell_color_x, &rd->cursor_fg, &rd->cursor_bg, rd->default_fg, rd->bg_colors0);
@@ -441,15 +462,9 @@ cell_update_uniform_block(ssize_t vao_idx, Screen *screen, int uniform_buffer, c
         }
         // store last rendered cursor color for trail rendering
         screen->last_rendered.cursor_bg = rd->cursor_bg;
-    } else rd->cursor_x = screen->columns, rd->cursor_y = screen->lines;
+    } else {
-    rd->cursor_w = rd->cursor_x;
+        rd->cursor_x1 = screen->columns + 1; rd->cursor_x2 = screen->columns;
-    const CPUCell *cursor_cell;
+        rd->cursor_y1 = screen->lines + 1; rd->cursor_y2 = screen->lines;
-    if (
-            (rd->cursor_fg_sprite_idx == BLOCK_IDX || rd->cursor_fg_sprite_idx == UNDERLINE_IDX) &&
-            line_for_cursor && (cursor_cell = line_for_cursor->cpu_cells + cursor->x)->is_multicell &&
-            cursor_cell->x == 0
-    ) {
-        rd->cursor_w = mcd_x_limit(cursor_cell);
     }
 
     rd->xnum = screen->columns; rd->ynum = screen->lines;

kitty_tests/multicell.py

@@ -2,7 +2,7 @@
 # License: GPLv3 Copyright: 2024, Kovid Goyal <kovid at kovidgoyal.net>
 
 
-from kitty.fast_data_types import TEXT_SIZE_CODE, wcswidth, test_ch_and_idx
+from kitty.fast_data_types import TEXT_SIZE_CODE, test_ch_and_idx, wcswidth
 
 from . import BaseTest, parse_bytes
 from . import draw_multicell as multicell