add shm_buffer class

meson.build

@@ -10,6 +10,7 @@ subdir('protocols')
 
 executable('somebar',
   'src/main.cpp',
+  'src/shm_buffer.cpp',
   wayland_sources,
   #moc,
   dependencies: [qt5_dep, wayland_dep])

src/bar.hpp

@@ -0,0 +1,16 @@
+// somebar - dwl bar
+// See LICENSE file for copyright and license details.
+
+#pragma once
+#include <wayland-client.h>
+#include "wlr-layer-shell-unstable-v1-client-protocol.h"
+#include "common.hpp"
+#include "shm_buffer.hpp"
+
+class Bar {
+    wl_surface *_surface {nullptr};
+    zwlr_layer_surface_v1 *_layerSurface {nullptr};
+    ShmBuffer _bufs;
+public:
+    explicit Bar(wl_output *output);
+};

src/common.hpp

@@ -0,0 +1,13 @@
+// somebar - dwl bar
+// See LICENSE file for copyright and license details.
+
+#pragma once
+#include <wayland-client.h>
+#include "wlr-layer-shell-unstable-v1-client-protocol.h"
+
+void waylandFlush();
+
+extern wl_display *display;
+extern wl_compositor *compositor;
+extern wl_shm *shm;
+extern zwlr_layer_shell_v1 *wlrLayerShell;

src/main.cpp

@@ -11,18 +11,18 @@
 #include "qnamespace.h"
 #include "wlr-layer-shell-unstable-v1-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
+#include "common.hpp"
+#include "shm_buffer.hpp"
 
 constexpr uint32_t barSize = 20;
 
-static void waylandFlush();
 static void waylandWriteReady();
 static void requireGlobal(const void *p, const char *name);
 
-// wayland globals
+wl_display *display;
-static wl_display *display;
+wl_compositor *compositor;
-static wl_compositor *compositor;
+wl_shm *shm;
-static wl_shm *shm;
+zwlr_layer_shell_v1 *wlrLayerShell;
-static zwlr_layer_shell_v1 *wlrLayerShell;
 static QSocketNotifier *displayWriteNotifier;
 
 static xdg_wm_base *xdgWmBase;
@@ -33,37 +33,25 @@ static const struct xdg_wm_base_listener xdgWmBaseListener = {
     }
 };
 
-static const struct wl_buffer_listener wlBufferListener {
-    [](void*, wl_buffer *buffer) {
-        wl_buffer_destroy(buffer);
-    }
-};
-
 // app globals
 static wl_surface *surface;
 static zwlr_layer_surface_v1 *layerSurface;
 static const struct wl_surface_listener surfaceListener = {
     // todo
 };
+static ShmBuffer *xbuf;
 static const struct zwlr_layer_surface_v1_listener layerSurfaceListener = {
     [](void*, zwlr_layer_surface_v1 *layerSurface, uint32_t serial, uint32_t width, uint32_t height) {
         zwlr_layer_surface_v1_ack_configure(layerSurface, serial);
         printf("configured to %d x %d\n", width, height);
-        auto stride = width * 4;
+        xbuf = new ShmBuffer(width, height, WL_SHM_FORMAT_XRGB8888);
-        auto size = stride * height;
+        auto buffer = xbuf->data();
-        auto fd = memfd_create("somebar-surface", MFD_CLOEXEC);
-        ftruncate(fd, size);
-        auto buffer = reinterpret_cast<char*>(mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
-        auto pool = wl_shm_create_pool(shm, fd, size);
-        auto wlBuffer = wl_shm_pool_create_buffer(pool, 0, width, height, stride, WL_SHM_FORMAT_XRGB8888);
-        wl_shm_pool_destroy(pool);
-        close(fd);
 
         auto w = 2*M_PI/(width / 10);
         for (auto x = 0; x < width; x++) {
             auto val = 255*(sin(x*w)/2+0.5);
             for (auto y = 0; y < height; y++) {
-                auto p = &buffer[y*stride+x*4];
+                auto p = &buffer[y*xbuf->stride+x*4];
                 *p++ = 0;
                 *p++ = 0;
                 *p++ = val;
@@ -71,8 +59,7 @@ static const struct zwlr_layer_surface_v1_listener layerSurfaceListener = {
             }
         }
 
-        wl_buffer_add_listener(wlBuffer, &wlBufferListener, nullptr);
+        wl_surface_attach(surface, xbuf->buffer(), 0, 0);
-        wl_surface_attach(surface, wlBuffer, 0, 0);
         wl_surface_commit(surface);
         waylandFlush();
     }
@@ -156,7 +143,7 @@ int main(int argc, char **argv)
     return app.exec();
 }
 
-static void waylandFlush()
+void waylandFlush()
 {
     wl_display_dispatch_pending(display);
     if (wl_display_flush(display) < 0 && errno == EAGAIN) {

src/shm_buffer.cpp

@@ -0,0 +1,42 @@
+// somebar - dwl bar
+// See LICENSE file for copyright and license details.
+
+#include <sys/mman.h>
+#include <unistd.h>
+#include "shm_buffer.hpp"
+#include "common.hpp"
+
+constexpr int n = 2;
+
+ShmBuffer::ShmBuffer(int w, int h, wl_shm_format format)
+    : width(w)
+    , height(h)
+    , stride(w*4)
+{
+    auto oneSize = stride*h;
+    _totalSize = oneSize * n;
+    auto fd = memfd_create("wl_shm", MFD_CLOEXEC);
+    ftruncate(fd, _totalSize);
+    auto pool = wl_shm_create_pool(shm, fd, _totalSize);
+    auto ptr = reinterpret_cast<char*>(mmap(nullptr, _totalSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
+    close(fd);
+    for (auto i=0; i<n; i++) {
+        auto offset = oneSize*i;
+        auto buffer = wl_shm_pool_create_buffer(pool, offset, width, height, stride, format);
+        _buffers[i] = { ptr+offset, buffer };
+    }
+    wl_shm_pool_destroy(pool);
+}
+
+ShmBuffer::~ShmBuffer()
+{
+    munmap(_buffers[0].data, _totalSize);
+    for (auto i=0; i<n; i++) {
+        wl_buffer_destroy(_buffers[i].buffer);
+    }
+    waylandFlush();
+}
+
+char* ShmBuffer::data() const { return _buffers[_current].data; }
+wl_buffer* ShmBuffer::buffer() const { return _buffers[_current].buffer; }
+void ShmBuffer::flip() { _current = 1-_current; }

src/shm_buffer.hpp

@@ -0,0 +1,25 @@
+// somebar - dwl bar
+// See LICENSE file for copyright and license details.
+
+#pragma once
+#include <array>
+#include <wayland-client.h>
+
+// double buffered shm
+// format is must be 32-bit
+class ShmBuffer {
+    struct Buf {
+        char *data {nullptr};
+        wl_buffer *buffer {nullptr};
+    };
+    std::array<Buf, 2> _buffers;
+    int _current {0};
+    size_t _totalSize {0};
+public:
+    int width, height, stride;
+    explicit ShmBuffer(int width, int height, wl_shm_format format);
+    char* data() const;
+    wl_buffer* buffer() const;
+    void flip();
+    ~ShmBuffer();
+};