From 3eb32cf75051f79060e576ab413ec35e9d05f633 Mon Sep 17 00:00:00 2001
From: Daniel van Vugt <daniel.van.vugt@canonical.com>
Date: Thu, 25 Jul 2024 19:08:11 +0800
Subject: [PATCH] cogl/tests: Avoid floats when converting between int formats

All we need is an intermediate int format with twice as many bits and
to put division at the end to avoid any loss of precision.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3903>
---
 .../cogl/conform/test-offscreen-texture-formats.c      | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/tests/cogl/conform/test-offscreen-texture-formats.c b/src/tests/cogl/conform/test-offscreen-texture-formats.c
index 23eee3538..ba2d804c1 100644
--- a/src/tests/cogl/conform/test-offscreen-texture-formats.c
+++ b/src/tests/cogl/conform/test-offscreen-texture-formats.c
@@ -35,19 +35,13 @@ get_bits (uint32_t in,
 static int
 rgb16_to_rgb8 (int rgb16)
 {
-  float r;
-
-  r = rgb16 / (float) ((1 << 16) - 1);
-  return (int) (r * (float) ((1 << 8) - 1));
+  return (int) ((int32_t) rgb16 * 0xff / 0xffff);
 }
 
 static int
 rgb8_to_rgb16 (int rgb8)
 {
-  float r;
-
-  r = rgb8 / (float) ((1 << 8) - 1);
-  return (int) (r * (float) ((1 << 16) - 1));
+  return (int) ((int32_t) rgb8 * 0xffff / 0xff);
 }
 
 static void