web browser (Servo)
git clone https://git.lucas.co/cce-browser.git
spike/wpe-spike.c (7.7K)
1 /*
2 * WPE embedding spike — reference, NOT part of the build.
3 *
4 * Proves the whole embedding contract WPE-PORT.md plans against: own the
5 * display, own the view, own the toplevel, and get rendered pixels out as a
6 * CPU-mappable buffer. Verified 2026-08-27 against wpewebkit 2.52.6-1 —
7 * renders example.com pixel-correct at 1200x800.
8 *
9 * gcc -Wno-deprecated-declarations spike/wpe-spike.c -o /tmp/wpe-spike \
10 * $(pkg-config --cflags --libs wpe-webkit-2.0 wpe-platform-2.0)
11 * /tmp/wpe-spike https://example.com # writes /tmp/wpe-spike.ppm
12 *
13 * It is C because the point was to settle the object graph fast, before
14 * paying for bindgen and GObject subclassing from Rust. Keep it as the
15 * thing to read while writing that; the two traps below cost hours and
16 * neither produces an error message.
17 *
18 * TRAP 1 — the toplevel owns format negotiation. WebKit asks
19 * WPEToplevelClass.get_preferred_buffer_formats, NOT the display's. Leave
20 * WPEDisplayClass.create_toplevel NULL and render_buffer never fires, with
21 * no warning and a perfectly healthy web process.
22 *
23 * TRAP 2 — the buffer handshake has two halves. wpe_view_buffer_rendered
24 * means "displayed"; wpe_view_buffer_released means "the memory is yours
25 * again". Call only the first and you get exactly one frame, then a
26 * permanent stall. This is also the backpressure that makes the unbounded
27 * upload queue of the Servo path impossible here.
28 */
29 #include <wpe/webkit.h>
30 #include <wpe/wpe-platform.h>
31 #include <stdio.h>
32
33 static GMainLoop *loop;
34 static int frames = 0;
35
36 /* ---- our WPEView: receives rendered buffers ---- */
37 #define SPIKE_TYPE_VIEW (spike_view_get_type())
38 G_DECLARE_FINAL_TYPE(SpikeView, spike_view, SPIKE, VIEW, WPEView)
39 struct _SpikeView { WPEView parent; };
40 G_DEFINE_TYPE(SpikeView, spike_view, WPE_TYPE_VIEW)
41
42 static gboolean spike_view_render_buffer(WPEView *view, WPEBuffer *buffer,
43 const WPERectangle *damage, guint n_damage,
44 GError **error) {
45 int w = wpe_buffer_get_width(buffer), h = wpe_buffer_get_height(buffer);
46 const char *kind = WPE_IS_BUFFER_SHM(buffer) ? "SHM"
47 : (WPE_IS_BUFFER_DMA_BUF(buffer) ? "DMABuf" : "other");
48 printf("render_buffer #%d: %dx%d type=%s damage_rects=%u\n",
49 ++frames, w, h, kind, n_damage);
50
51 if (WPE_IS_BUFFER_SHM(buffer)) {
52 WPEBufferSHM *shm = WPE_BUFFER_SHM(buffer);
53 GBytes *bytes = wpe_buffer_shm_get_data(shm);
54 gsize len = 0; const guchar *px = g_bytes_get_data(bytes, &len);
55 guint stride = wpe_buffer_shm_get_stride(shm);
56 printf(" bytes=%zu stride=%u format=%d\n", len, stride,
57 (int)wpe_buffer_shm_get_format(shm));
58 if (frames == 2) { // let the page settle a little
59 FILE *f = fopen("/tmp/wpe-spike.ppm", "wb");
60 fprintf(f, "P6\n%d %d\n255\n", w, h);
61 for (int y = 0; y < h; y++)
62 for (int x = 0; x < w; x++) {
63 const guchar *p = px + y * stride + x * 4; // BGRA
64 fputc(p[2], f); fputc(p[1], f); fputc(p[0], f);
65 }
66 fclose(f);
67 printf(" WROTE /tmp/wpe-spike.ppm\n");
68 g_main_loop_quit(loop);
69 }
70 }
71 // Both halves of the handshake: displayed, then memory returned.
72 wpe_view_buffer_rendered(view, buffer);
73 wpe_view_buffer_released(view, buffer);
74 return TRUE;
75 }
76 static void spike_view_init(SpikeView *v) {}
77 static void spike_view_class_init(SpikeViewClass *k) {
78 WPE_VIEW_CLASS(k)->render_buffer = spike_view_render_buffer;
79 }
80
81 /* ---- our WPEToplevel: WebKit asks IT for buffer formats ---- */
82 #define SPIKE_TYPE_TOPLEVEL (spike_toplevel_get_type())
83 G_DECLARE_FINAL_TYPE(SpikeToplevel, spike_toplevel, SPIKE, TOPLEVEL, WPEToplevel)
84 struct _SpikeToplevel { WPEToplevel parent; };
85 G_DEFINE_TYPE(SpikeToplevel, spike_toplevel, WPE_TYPE_TOPLEVEL)
86
87 #define FOURCC(a,b,c,d) ((guint32)(a)|((guint32)(b)<<8)|((guint32)(c)<<16)|((guint32)(d)<<24))
88 static WPEBufferFormats *spike_toplevel_formats(WPEToplevel *t) {
89 WPEBufferFormatsBuilder *b = wpe_buffer_formats_builder_new(NULL);
90 wpe_buffer_formats_builder_append_group(b, NULL, WPE_BUFFER_FORMAT_USAGE_MAPPING);
91 wpe_buffer_formats_builder_append_format(b, FOURCC('A','R','2','4'), 0);
92 wpe_buffer_formats_builder_append_format(b, FOURCC('X','R','2','4'), 0);
93 return wpe_buffer_formats_builder_end(b);
94 }
95 static gboolean spike_toplevel_resize(WPEToplevel *t, int w, int h) {
96 printf("toplevel resize -> %dx%d\n", w, h);
97 wpe_toplevel_resized(t, w, h);
98 return TRUE;
99 }
100 static void spike_toplevel_init(SpikeToplevel *t) {}
101 static void spike_toplevel_class_init(SpikeToplevelClass *k) {
102 WPEToplevelClass *tc = WPE_TOPLEVEL_CLASS(k);
103 tc->get_preferred_buffer_formats = spike_toplevel_formats;
104 tc->resize = spike_toplevel_resize;
105 }
106
107 /* ---- our WPEDisplay: vends the view above ---- */
108 #define SPIKE_TYPE_DISPLAY (spike_display_get_type())
109 G_DECLARE_FINAL_TYPE(SpikeDisplay, spike_display, SPIKE, DISPLAY, WPEDisplay)
110 struct _SpikeDisplay { WPEDisplay parent; };
111 G_DEFINE_TYPE(SpikeDisplay, spike_display, WPE_TYPE_DISPLAY)
112
113 static gboolean spike_display_connect(WPEDisplay *d, GError **e) { return TRUE; }
114
115 #define FOURCC(a,b,c,d) ((guint32)(a)|((guint32)(b)<<8)|((guint32)(c)<<16)|((guint32)(d)<<24))
116 /* No EGL display and no DRM device -> WebKit should fall back to mappable SHM.
117 Advertise ARGB/XRGB with LINEAR so it has something to pick. */
118 static WPEBufferFormats *spike_display_formats(WPEDisplay *d) {
119 WPEBufferFormatsBuilder *b = wpe_buffer_formats_builder_new(NULL);
120 wpe_buffer_formats_builder_append_group(b, NULL, WPE_BUFFER_FORMAT_USAGE_RENDERING);
121 wpe_buffer_formats_builder_append_format(b, FOURCC('A','B','2','4'), 0 /*LINEAR*/);
122 wpe_buffer_formats_builder_append_format(b, FOURCC('X','B','2','4'), 0);
123 return wpe_buffer_formats_builder_end(b);
124 }
125 static WPEView *spike_display_create_view(WPEDisplay *d) {
126 return g_object_new(SPIKE_TYPE_VIEW, "display", d, NULL);
127 }
128 static WPEToplevel *spike_display_create_toplevel(WPEDisplay *d, guint max_views) {
129 printf("create_toplevel(max_views=%u)\n", max_views);
130 return g_object_new(SPIKE_TYPE_TOPLEVEL, "display", d, "max-views", max_views, NULL);
131 }
132 static void spike_display_init(SpikeDisplay *d) {}
133 static void spike_display_class_init(SpikeDisplayClass *k) {
134 WPEDisplayClass *dc = WPE_DISPLAY_CLASS(k);
135 dc->connect = spike_display_connect;
136 dc->create_view = spike_display_create_view;
137 dc->get_preferred_buffer_formats = spike_display_formats;
138 dc->create_toplevel = spike_display_create_toplevel;
139 }
140
141 int main(int argc, char **argv) {
142 const char *url = argc > 1 ? argv[1] : "https://example.com";
143 WPEDisplay *display = g_object_new(SPIKE_TYPE_DISPLAY, NULL);
144 GError *err = NULL;
145 if (!wpe_display_connect(display, &err)) {
146 printf("connect failed: %s\n", err ? err->message : "?"); return 1;
147 }
148 WebKitWebView *wv = g_object_new(WEBKIT_TYPE_WEB_VIEW, "display", display, NULL);
149 WPEView *v = webkit_web_view_get_wpe_view(wv);
150 printf("web view=%p its wpe_view=%p\n", (void*)wv, (void*)v);
151 WPEToplevel *top = wpe_display_create_toplevel(display, 1);
152 printf("toplevel=%p\n", (void*)top);
153 if (top) { wpe_toplevel_resized(top, 1200, 800); wpe_view_set_toplevel(v, top); }
154 wpe_view_resized(v, 1200, 800);
155 wpe_view_set_visible(v, TRUE);
156 wpe_view_map(v);
157 printf("view now %dx%d visible=%d mapped=%d\n", wpe_view_get_width(v),
158 wpe_view_get_height(v), wpe_view_get_visible(v), wpe_view_get_mapped(v));
159 webkit_web_view_load_uri(wv, url);
160 loop = g_main_loop_new(NULL, FALSE);
161 g_timeout_add_seconds(25, (GSourceFunc)g_main_loop_quit, loop);
162 g_main_loop_run(loop);
163 printf("done, %d frames\n", frames);
164 return frames ? 0 : 2;
165 }