From 11badac95db3677b5224932847e5c656c9b1ef8b Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 5 Dec 2021 18:26:25 +0530
Subject: [PATCH] Ensure cell start position is clamped to a pixel

---
 kitty/graphics.h | 12 ++++++++++++
 kitty/state.c    |  4 ++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/kitty/graphics.h b/kitty/graphics.h
index daad0bb45..760f8f272 100644
--- a/kitty/graphics.h
+++ b/kitty/graphics.h
@@ -138,6 +138,18 @@ clamp_position_to_nearest_pixel(float pos, const unsigned int viewport_size) {
     return -1.f + num_of_pixels * px;
 }
 
+static inline float
+gl_pos_x(const unsigned int px_from_left_margin, const unsigned int viewport_size) {
+    const float px = 2.f / viewport_size;
+    return -1.f + px_from_left_margin * px;
+}
+
+static inline float
+gl_pos_y(const unsigned int px_from_top_margin, const unsigned int viewport_size) {
+    const float px = 2.f / viewport_size;
+    return 1.f - px_from_top_margin * px;
+}
+
 
 GraphicsManager* grman_alloc(void);
 void grman_clear(GraphicsManager*, bool, CellPixelSize fg);
diff --git a/kitty/state.c b/kitty/state.c
index 57ff6e3cd..0b50c83c2 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -709,8 +709,8 @@ static void
 init_screen_render_data(OSWindow *osw, const WindowGeometry *g, ScreenRenderData *d) {
     d->dx = gl_size(osw->fonts_data->cell_width, osw->viewport_width);
     d->dy = gl_size(osw->fonts_data->cell_height, osw->viewport_height);
-    d->xstart = -1.f + gl_size(g->left, osw->viewport_width);
-    d->ystart = 1.f - gl_size(g->top, osw->viewport_height);
+    d->xstart = gl_pos_x(g->left, osw->viewport_width);
+    d->ystart = gl_pos_y(g->top, osw->viewport_height);
 }
 
 PYWRAP1(set_tab_bar_render_data) {