perf: prevent expensive nvim_win_text_height call on big scroll

Author: sphamba

lua/smear_cursor/animation.lua

@@ -521,7 +521,7 @@ end
 local function scroll_buffer_space()
 	if current_top_row ~= previous_top_row and current_line ~= previous_line then
 		-- Shift to show smear in buffer space instead of screen space
-		local shift = screen.get_screen_distance(previous_top_row, current_top_row)
+		local shift = screen.get_screen_distance(previous_top_row, current_top_row, current_window_id)
 		local shifted_position = { current_corners[1][1] - shift, current_corners[1][2] }
 		clamp_to_buffer(shifted_position)
 		set_corners(current_corners, shifted_position[1], shifted_position[2])

lua/smear_cursor/screen.lua

@@ -36,24 +36,30 @@ M.get_screen_cmd_cursor_position = function()
 	return row, col
 end
 
-M.get_screen_distance = function(row_start, row_end)
+M.get_screen_distance = function(row_start, row_end, window_id)
 	local reversed = false
 
 	if row_start > row_end then
 		row_start, row_end = row_end, row_start
 		reversed = true
 	end
 
+	local window_height = vim.api.nvim_win_get_height(window_id)
+
 	local text_height
-	local success = pcall(function()
-		text_height = vim.api.nvim_win_text_height(0, {
-			start_row = row_start - 1,
-			end_row = row_end - 1,
-		})
-	end)
-
-	if not success then -- line is not visible
-		text_height = { all = 1 }
+	if row_end - row_start >= window_height then
+		text_height = { all = window_height }
+	else
+		local success = pcall(function()
+			text_height = vim.api.nvim_win_text_height(0, {
+				start_row = row_start - 1,
+				end_row = row_end - 1,
+			})
+		end)
+
+		if not success then -- line is not visible
+			text_height = { all = 1 }
+		end
 	end
 
 	local distance = text_height.all - 1