Implement VNC backend

Add VNC backend using `neatvnc`[1]. Allow users can view and interact
with applications in Mado through VNC-compatible client software.

[1]: https://github.com/any1/neatvnc

Close #32

Makefile

@@ -110,6 +110,13 @@ libtwin.a_files-y += backend/fbdev.c
 libtwin.a_files-y += backend/linux_input.c
 endif
 
+ifeq ($(CONFIG_BACKEND_VNC), y)
+BACKEND = vnc
+libtwin.a_files-y += backend/vnc.c
+libtwin.a_cflags-y += $(shell pkg-config --cflags neatvnc aml pixman-1)
+TARGET_LIBS += $(shell pkg-config --libs neatvnc aml pixman-1)
+endif
+
 # Standalone application
 
 ifeq ($(CONFIG_DEMO_APPLICATIONS), y)

README.md

@@ -70,6 +70,11 @@ and the [SDL2 library](https://www.libsdl.org/).
 * macOS: `brew install sdl2 jpeg libpng`
 * Ubuntu Linux / Debian: `sudo apt install libsdl2-dev libjpeg-dev libpng-dev`
 
+Please note that the VNC backend is only tested on GNU/Linux, and the prebuilt [neatvnc](https://github.com/any1/neatvnc) package might be outdated. To ensure you have the latest versions, you can build the dependent packages from source by running the script:
+```bash
+$ tools/build-neatvnc.sh
+```
+
 ### Configuration
 
 Configure via [Kconfiglib](https://pypi.org/project/kconfiglib/), you should select either SDL
@@ -108,6 +113,14 @@ $ sudo usermod -a -G video $USERNAME
 
 In addition, the framebuffer device can be assigned via the environment variable `FRAMEBUFFER`.
 
+To run demo program with the neat-vnc backend:
+
+```shell
+$ ./demo-vnc
+```
+
+It would launch the vnc server. You could use any VNC client to connect with given IP address(default is "127.0.0.1") and port (default is 5900), you could assign the IP address via the environment variable `MADO_VNC_HOST` and the port via `MADO_VNC_PORT`
+
 ## License
 
 `Mado` is available under a MIT-style license, permitting liberal commercial use.

backend/vnc.c

@@ -0,0 +1,272 @@
+/*
+Twin - A Tiny Window System
+Copyright (c) 2024 National Cheng Kung University, Taiwan
+All rights reserved.
+*/
+#define AML_UNSTABLE_API 1
+#include <aml.h>
+#include <assert.h>
+#include <neatvnc.h>
+#include <pixman.h>
+#include <stdlib.h>
+#include <string.h>
+#include <twin.h>
+
+#include "twin_backend.h"
+#include "twin_private.h"
+
+#define SCREEN(x) ((twin_context_t *) x)->screen
+#define PRIV(x) ((twin_vnc_t *) ((twin_context_t *) x)->priv)
+#define MADO_VNC_HOST "MADO_VNC_HOST"
+#define MADO_VNC_PORT "MADO_VNC_PORT"
+#define MADO_VNC_HOST_DEFAULT "127.0.0.1"
+#define MADO_VNC_PORT_DEFAULT "5900"
+
+#ifndef DRM_FORMAT_ARGB8888
+#define fourcc_code(a, b, c, d)                                        \
+    ((uint32_t) (a) | ((uint32_t) (b) << 8) | ((uint32_t) (c) << 16) | \
+     ((uint32_t) (d) << 24))
+#define DRM_FORMAT_ARGB8888 fourcc_code('A', 'R', '2', '4')
+#endif
+
+typedef struct {
+    twin_screen_t *screen;
+    struct aml *aml;
+    struct aml_handler *aml_handler;
+    struct nvnc *server;
+    struct nvnc_display *display;
+    struct nvnc_fb *current_fb;
+    struct pixman_region16 damage_region;
+    uint32_t *framebuffer;
+    int width;
+    int height;
+} twin_vnc_t;
+
+typedef struct {
+    uint16_t px, py;
+    enum nvnc_button_mask prev_button;
+} twin_peer_t;
+
+static void _twin_vnc_put_begin(twin_coord_t left,
+                                twin_coord_t top,
+                                twin_coord_t right,
+                                twin_coord_t bottom,
+                                void *closure)
+{
+    (void) left;
+    (void) top;
+    (void) right;
+    (void) bottom;
+    twin_vnc_t *tx = PRIV(closure);
+    pixman_region_init_rect(&tx->damage_region, 0, 0, tx->width, tx->height);
+}
+
+static void _twin_vnc_put_span(twin_coord_t left,
+                               twin_coord_t top,
+                               twin_coord_t right,
+                               twin_argb32_t *pixels,
+                               void *closure)
+{
+    twin_vnc_t *tx = PRIV(closure);
+    uint32_t *fb_pixels = tx->framebuffer + top * tx->width + left;
+    size_t span_width = right - left;
+
+    memcpy(fb_pixels, pixels, span_width * sizeof(*fb_pixels));
+
+    pixman_region_init_rect(&tx->damage_region, left, top, span_width, 1);
+
+    if (pixman_region_not_empty(&tx->damage_region)) {
+        nvnc_display_feed_buffer(tx->display, tx->current_fb,
+                                 &tx->damage_region);
+        pixman_region_clear(&tx->damage_region);
+    }
+    aml_poll(tx->aml, 0);
+    aml_dispatch(tx->aml);
+}
+
+static void twin_vnc_get_screen_size(twin_vnc_t *tx, int *width, int *height)
+{
+    *width = nvnc_fb_get_width(tx->current_fb);
+    *height = nvnc_fb_get_height(tx->current_fb);
+}
+
+static bool _twin_vnc_work(void *closure)
+{
+    twin_screen_t *screen = SCREEN(closure);
+
+    if (twin_screen_damaged(screen))
+        twin_screen_update(screen);
+    return true;
+}
+
+static void _twin_vnc_new_client(struct nvnc_client *client)
+{
+    twin_peer_t *peer = malloc(sizeof(twin_peer_t));
+    nvnc_set_userdata(client, peer, NULL);
+}
+
+static bool _twin_vnc_read_events(int fd, twin_file_op_t op, void *closure)
+{
+    (void) fd;
+    (void) op;
+    (void) closure;
+    return true;
+}
+
+static void _twin_vnc_pointer_event(struct nvnc_client *client,
+                                    uint16_t x,
+                                    uint16_t y,
+                                    enum nvnc_button_mask button)
+{
+    twin_peer_t *peer = nvnc_get_userdata(client);
+    twin_event_t tev;
+    if ((button & NVNC_BUTTON_LEFT) &&
+        !(peer->prev_button & NVNC_BUTTON_LEFT)) {
+        tev.u.pointer.screen_x = x;
+        tev.u.pointer.screen_y = y;
+        tev.kind = TwinEventButtonDown;
+        tev.u.pointer.button = 1;
+    } else if (!(button & NVNC_BUTTON_LEFT) &&
+               (peer->prev_button & NVNC_BUTTON_LEFT)) {
+        tev.u.pointer.screen_x = x;
+        tev.u.pointer.screen_y = y;
+        tev.kind = TwinEventButtonUp;
+        tev.u.pointer.button = 1;
+    }
+    if ((peer->px != x || peer->py != y)) {
+        peer->px = x;
+        peer->py = y;
+        tev.u.pointer.screen_x = x;
+        tev.u.pointer.screen_y = y;
+        tev.u.pointer.button = 0;
+        tev.kind = TwinEventMotion;
+    }
+    peer->prev_button = button;
+    struct nvnc *server = nvnc_client_get_server(client);
+    twin_vnc_t *tx = nvnc_get_userdata(server);
+    twin_screen_dispatch(tx->screen, &tev);
+}
+
+twin_context_t *twin_vnc_init(int width, int height)
+{
+    twin_context_t *ctx = calloc(1, sizeof(twin_context_t));
+    if (!ctx)
+        return NULL;
+    ctx->priv = calloc(1, sizeof(twin_vnc_t));
+    if (!ctx->priv) {
+        free(ctx);
+        return NULL;
+    }
+
+    twin_vnc_t *tx = ctx->priv;
+    tx->width = width;
+    tx->height = height;
+
+    tx->aml = aml_new();
+    if (!tx->aml) {
+        log_error("Failed to create aml");
+        goto bail_priv;
+    }
+    aml_set_default(tx->aml);
+    char *vnc_host = getenv(MADO_VNC_HOST);
+    if (!vnc_host) {
+        log_info(
+            "Environment variable $MADO_VNC_HOST not set, use %s by default",
+            MADO_VNC_HOST_DEFAULT);
+        vnc_host = MADO_VNC_HOST_DEFAULT;
+    }
+    char *vnc_port = getenv(MADO_VNC_PORT);
+    if (!vnc_port) {
+        log_info(
+            "Environment variable $MADO_VNC_PORT not set, use %s by default",
+            MADO_VNC_PORT_DEFAULT);
+        vnc_port = MADO_VNC_PORT_DEFAULT;
+    }
+    log_info("NeatVNC server IP %s PORT %s", vnc_host, vnc_port);
+    tx->server = nvnc_open(vnc_host, atoi(vnc_port));
+    if (!tx->server) {
+        log_error("Failed to open neatvnc server");
+        goto bail_aml;
+    }
+
+    tx->display = nvnc_display_new(0, 0);
+    if (!tx->display) {
+        log_error("Failed to create neatvnc display");
+        goto bail_server;
+    }
+
+    nvnc_add_display(tx->server, tx->display);
+    nvnc_set_name(tx->server, "Twin VNC Backend");
+    nvnc_set_pointer_fn(tx->server, _twin_vnc_pointer_event);
+    nvnc_set_new_client_fn(tx->server, _twin_vnc_new_client);
+    nvnc_set_userdata(tx->server, tx, NULL);
+
+    ctx->screen = twin_screen_create(width, height, _twin_vnc_put_begin,
+                                     _twin_vnc_put_span, ctx);
+    if (!ctx->screen)
+        goto bail_display;
+
+    tx->framebuffer = calloc(width * height, sizeof(uint32_t));
+    if (!tx->framebuffer) {
+        log_error("Failed to allocate framebuffer");
+        goto bail_screen;
+    }
+
+    tx->current_fb = nvnc_fb_from_buffer(tx->framebuffer, width, height,
+                                         DRM_FORMAT_ARGB8888, width);
+    if (!tx->current_fb) {
+        log_error("Failed to init VNC framebuffer");
+        goto bail_framebuffer;
+    }
+    int aml_fd = aml_get_fd(tx->aml);
+    twin_set_file(_twin_vnc_read_events, aml_fd, TWIN_READ, tx);
+
+    twin_set_work(_twin_vnc_work, TWIN_WORK_REDISPLAY, ctx);
+    tx->screen = ctx->screen;
+
+    return ctx;
+
+bail_framebuffer:
+    free(tx->framebuffer);
+bail_screen:
+    twin_screen_destroy(ctx->screen);
+bail_display:
+    nvnc_display_unref(tx->display);
+bail_server:
+    nvnc_close(tx->server);
+bail_aml:
+    aml_unref(tx->aml);
+bail_priv:
+    free(ctx->priv);
+    free(ctx);
+    return NULL;
+}
+
+static void twin_vnc_configure(twin_context_t *ctx)
+{
+    int width, height;
+    twin_vnc_t *tx = ctx->priv;
+    twin_vnc_get_screen_size(tx, &width, &height);
+    twin_screen_resize(ctx->screen, width, height);
+}
+
+static void twin_vnc_exit(twin_context_t *ctx)
+{
+    if (!ctx)
+        return;
+
+    twin_vnc_t *tx = PRIV(ctx);
+
+    nvnc_display_unref(tx->display);
+    nvnc_close(tx->server);
+    aml_unref(tx->aml);
+
+    free(ctx->priv);
+    free(ctx);
+}
+
+const twin_backend_t g_twin_backend = {
+    .init = twin_vnc_init,
+    .configure = twin_vnc_configure,
+    .exit = twin_vnc_exit,
+};

configs/Kconfig

@@ -15,6 +15,8 @@ config BACKEND_FBDEV
 config BACKEND_SDL
     bool "SDL video output support"
 
+config BACKEND_VNC
+    bool "VNC server output support"
 endchoice
 
 menu "Features"

tools/build-neatvnc.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+# Update and install dependencies
+sudo apt update
+sudo apt install -y meson ninja-build libpixman-1-dev zlib1g-dev libdrm-dev pkg-config
+
+TOP_DIR=$(pwd)
+# Clone and build aml
+git clone https://github.com/any1/aml && pushd aml
+meson -Dprefix=$TOP_DIR/_static --default-library=static build
+ninja -C build install
+popd
+
+export PKG_CONFIG_PATH=$TOP_DIR/_static/lib/$(uname -m)-linux-gnu/pkgconfig
+
+# Clone and build NeatVNC
+git clone https://github.com/any1/neatvnc --depth=1 -b v0.8.1 && pushd neatvnc
+meson -Dprefix=$TOP_DIR/_static --default-library=static build
+ninja -C build install
+popd
+
+# Prompt for PKG_CONFIG_PATH
+echo "Now, statically-linked libraries of both aml and neatvnc were installed, and you can set PKG_CONFIG_PATH properly for the Mado build system to detect and facilitate."
+echo "For example, you can run:"
+echo "  export PKG_CONFIG_PATH=\$(pwd)/_static/lib/\$(uname -m)-linux-gnu/pkgconfig/"