From 71c72db1e35ae4ca7a0688e055aad3e4f193cb58 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jonas=20=C3=85dahl?= Date: Wed, 17 Feb 2016 13:51:08 +0800 Subject: [PATCH] wayland: Pre-multiply custom cursor image alpha Since the Wayland SHM buffer format is implicitly premultiplied and the GLFWimage pixels are defined to be non-premultiplied, we need to convert the non-premultiplied pixels to premultiplied when filling the buffer. Related to #707. --- src/internal.h | 7 +++++++ src/wl_window.c | 10 ++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/src/internal.h b/src/internal.h index 358da256..0e41fbd7 100644 --- a/src/internal.h +++ b/src/internal.h @@ -233,6 +233,13 @@ typedef VkResult (APIENTRY * PFN_vkEnumerateInstanceExtensionProperties)(const c y = t; \ } +// Helper for non-premultiplied alpha to premultiplied alpha conversion +static inline unsigned char _glfwMultiplyAlpha(unsigned char alpha, + unsigned char value) +{ + return (unsigned char) ((value * (unsigned int) alpha) / 255); +} + //======================================================================== // Platform-independent structures diff --git a/src/wl_window.c b/src/wl_window.c index 521dc3c2..ca91a2f5 100644 --- a/src/wl_window.c +++ b/src/wl_window.c @@ -588,10 +588,12 @@ int _glfwPlatformCreateCursor(_GLFWcursor* cursor, unsigned char* target = data; for (i = 0; i < image->width * image->height; i++, source += 4) { - *target++ = source[2]; - *target++ = source[1]; - *target++ = source[0]; - *target++ = source[3]; + unsigned char alpha = source[3]; + + *target++ = _glfwMultiplyAlpha(alpha, source[2]); + *target++ = _glfwMultiplyAlpha(alpha, source[1]); + *target++ = _glfwMultiplyAlpha(alpha, source[0]); + *target++ = alpha; } cursor->wl.buffer =