daniel/danos
1
0
Fork 0
Code Issues 4 Pull Requests Actions Packages Projects 1 Releases Wiki Activity

display-demo: stop drawing a cursor and stop blocking on the mouse

Browse Source 
Two real bugs visible in a normal `zig build run-x86-64` boot (but not in the
display-demo test, which spawns no input service):

  - Two cursors. The demo drew its own cursor layer while the display service
    now draws one too (its mouse-listener thread). The demo's went through the
    client IPC protocol and lagged; the service's is in-process and tracks
    tightly — "one responds better than the other."

  - Animation frozen until the mouse moves. The demo called a *blocking*
    `mouse.next()` (ipc_reply_wait) inside its animation loop, so the sliding
    box advanced only one frame per mouse event. In the display-demo test
    there is no input service, so subscribeMouse() returned null and the loop
    ran free on its 30ms timer — which is exactly why the test passed while
    the real boot was broken.

The compositor now owns the cursor (docs/display.md), so the demo should draw
none and read no input: it becomes a pure client-animation proof whose loop is
independent of the mouse. Removes its cursor layer, mouse subscription, and the
blocking read.

Also harden displayDemoTest to spawn the `input` service alongside the demo
(matching real boot): a client that blocks its animation loop on a mouse read
would now stall before `display-demo: ok` and fail the test, instead of
passing because no input service happened to be present.

Verified: display / display-service / display-demo / display-cursor all green.
This commit is contained in:
daniel
2026-07-21 02:37:47 +01:00
parent 7f415e724f
commit 5ab7263c9c
3 changed files with 21 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files
system/services/display-demo/display-demo.zig
+9 -32
View File
@@ -1,15 +1,19 @@
//! system/services/display-demo — a hardware-free client of the display service, the
//! `input-source` analog for the compositor. It creates a wallpaper, a rectangle it moves
//! each frame, and a small cursor, then drives the compositor in a present loop — proof
//! that a *separate process* can compose a moving scene through the display service over
//! IPC, exercising the layer client API and damage-driven present end to end
//! `input-source` analog for the compositor. It creates a wallpaper and a rectangle it
//! slides each frame, then drives the compositor in a present loop — proof that a
//! *separate process* can compose a moving scene through the display service over IPC,
//! exercising the layer client API and damage-driven present end to end
//! (docs/display.md). It logs `display-demo: ok` once it has driven a run of frames.
//!
//! It draws no cursor and reads no input: the on-screen cursor is the display service's
//! own, tracked by the service's mouse-listener thread (docs/display.md). The demo's job
//! is only to prove client-driven animation, so its loop runs on its own frame timer and
//! is deliberately independent of the mouse.
const runtime = @import("runtime");
const display = runtime.display;
const system = runtime.system;
const time = runtime.time;
const input = runtime.input;
pub fn main() void {
const mode = display.info() orelse {
@@ -28,15 +32,6 @@ pub fn main() void {
const box = display.createLayer(0, box_y, box_w, box_h, 1) orelse return createFailed();
_ = box.fill(0, 0, box_w, box_h, display.color(0xE0, 0x60, 0x40));
// A little cursor on top. Its position is signed (the layer API is i32) and clamped to
// the screen; mouse motion arrives as relative deltas we accumulate below.
var cursor_x: i32 = @intCast(mode.width / 2);
var cursor_y: i32 = @intCast(mode.height / 2);
const cursor_max_x: i32 = @as(i32, @intCast(mode.width)) - 12;
const cursor_max_y: i32 = @as(i32, @intCast(mode.height)) - 12;
const cursor = display.createLayer(cursor_x, cursor_y, 12, 12, 2) orelse return createFailed();
_ = cursor.fill(0, 0, 12, 12, display.color(0xF0, 0xF0, 0xF0));
_ = display.present();
_ = system.write("display-demo: scene up; animating\n");
@@ -45,18 +40,7 @@ pub fn main() void {
var dx: i32 = 8;
var frame: u32 = 0;
var mouse = input.subscribeMouse(); // type: ?input.MouseSubscriber
if (mouse == null) _ = system.write("display-demo: no mouse; animating without it\n");
while (true) : (frame += 1) {
if (mouse) |*ms| {
if (ms.next()) |event| {
cursor_x = clamp(cursor_x + event.dx, 0, cursor_max_x);
cursor_y = clamp(cursor_y + event.dy, 0, cursor_max_y);
_ = cursor.configure(cursor_x, cursor_y, 2, true);
}
}
x += dx;
if (x <= 0) {
x = 0;
@@ -74,13 +58,6 @@ pub fn main() void {
}
}
/// Clamp `v` to the inclusive range [lo, hi].
fn clamp(v: i32, lo: i32, hi: i32) i32 {
if (v < lo) return lo;
if (v > hi) return hi;
return v;
}
fn createFailed() void {
_ = system.write("display-demo: create failed\n");
}