fix: always remove extmarks to prevent flickering

lua/smear_cursor/config.lua

@@ -40,7 +40,7 @@ M.min_slope_vertical = 2
 
 M.color_levels = 16 -- Minimum 1
 M.gamma = 2.2 -- For color blending
-M.max_shade_no_matrix = 0.9 -- 0: more overhangs, 1: more matrices
+M.max_shade_no_matrix = 0.75 -- 0: more overhangs, 1: more matrices
 M.matrix_pixel_threshold = 0.5 -- 0: all pixels, 1: no pixel
 M.matrix_pixel_min_factor = 0.5 -- 0: all pixels, 1: no pixel
 M.volume_reduction_exponent = 0.3 -- 0: no reduction, 1: full reduction

lua/smear_cursor/draw.lua

@@ -116,10 +116,10 @@ M.clear = function()
 			local wb = tab_windows.windows[i]
 
 			if wb and vim.api.nvim_win_is_valid(wb.window_id) then
+				vim.api.nvim_buf_del_extmark(wb.buffer_id, cursor_namespace, extmark_id)
 				if can_hide then
 					vim.api.nvim_win_set_config(wb.window_id, { hide = true })
 				else
-					vim.api.nvim_buf_del_extmark(wb.buffer_id, cursor_namespace, extmark_id)
 					vim.api.nvim_win_set_config(wb.window_id, { relative = "editor", row = 0, col = 0 })
 				end
 			end
@@ -401,7 +401,8 @@ M.draw_quad = function(corners, target_position)
 			-- Draw shifted block
 			if is_vertically_shifted and is_horizontally_shifted then
 				if vertical_shade < config.max_shade_no_matrix and horizontal_shade < config.max_shade_no_matrix then
-					goto continue
+					is_horizontally_shifted = false
+					is_vertically_shifted = false
 				elseif vertical_shade < horizontal_shade then
 					is_horizontally_shifted = false
 				else

tests/test_draw_quad.lua

@@ -102,6 +102,18 @@ draw.draw_quad({
 	{ row + 5, col + 4 },
 })
 
+-- Degenerate quads (aligned points)
+
+row = 14
+col = 23
+
+draw.draw_quad({
+	{ row, col },
+	{ row - 1, col + 2 },
+	{ row + 3, col + 2 },
+	{ row + 3, col - 1 },
+})
+
 -- Lines
 
 row = 23