From 3c39c55676162f83ed2eaf2fee3ec41254abc638 Mon Sep 17 00:00:00 2001 From: Berke Güzel Date: Tue, 13 Oct 2026 16:25:52 +0300 Subject: Fill the hello window with an RGB gradient Red grows to the right, green downward, and blue fades as red grows. Rows now step by the frame's stride_bytes instead of assuming packed pixels. Co-Authored-By: Claude Opus 5.5 --- docs/getting-started.md | 4 ++-- examples/hello.c | 13 ++++++++++--- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/docs/getting-started.md b/docs/getting-started.md index 906d425..73af4ab 100644 --- a/docs/getting-started.md +++ b/docs/getting-started.md @@ -39,8 +39,8 @@ CPU pixel targets are presented through the system's Metal device; applications do not need to create or manage that device themselves. The complete beginner example is [hello.c](../examples/hello.c). It lets -`yasl_run()` create its window from `yasl_app_desc.window`, fills every pixel, -and presents inside a frame callback. +`yasl_run()` create its window from `yasl_app_desc.window`, fills every pixel +with an RGB gradient, and presents inside a frame callback. `yasl_run()` handles input delivery, display notifications, and cleanup. The [interactive window](../examples/simple_window.c) adds pointer input; the [tablet example](../examples/tablet.c) demonstrates retained application content, diff --git a/examples/hello.c b/examples/hello.c index 38a0cac..4c171ec 100644 --- a/examples/hello.c +++ b/examples/hello.c @@ -6,9 +6,16 @@ static bool failed; static void draw(void *ud, struct yasl_surface *surface, struct yasl_frame_context *frame) { (void)ud; - size_t count = (size_t)frame->size.x * frame->size.y; - for (size_t i = 0; i < count; i++) - frame->cpu.pixels[i] = 0xff306090; /* Opaque premultiplied ARGB. */ + int w = frame->size.x, h = frame->size.y; + for (int y = 0; y < h; y++) { + uint32_t *row = frame->cpu.pixels + (size_t)y * (frame->cpu.stride_bytes / 4); + for (int x = 0; x < w; x++) { + /* Red grows rightward, green downward, blue fades; opaque premultiplied ARGB. */ + uint32_t r = (uint32_t)(x * 255 / (w > 1 ? w - 1 : 1)); + uint32_t g = (uint32_t)(y * 255 / (h > 1 ? h - 1 : 1)); + row[x] = 0xff000000 | r << 16 | g << 8 | (255 - r); + } + } if (!yasl_frame_present_cpu(frame, NULL, 0)) { fprintf(stderr, "Could not present the draw target\n"); -- cgit v1.2.3