vnc: first working RFB client, sends raw frames to SDL window

.gitignore

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+/vnc-client/build
+/vnc-client/cgvm_vnc

README.md

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+Setting up the extra display and starting wayvnc
+
+```
+% swaymsg create_output
+% swaymsg output "HEADLESS-1" resolution 396x224
+% wayvnc -o HEADLESS-1
+```
+
+Compiling and starting the VNC client
+
+```
+% cd vnc-client
+% cmake -B build
+% make -C build
+% ./cgvm_vnc
+```

vnc-client/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.15)
+project(CGVirtualMonitorVNCClient VERSION 1.0 LANGUAGES C)
+
+find_package(LibVNCServer 0.9 REQUIRED)
+find_package(SDL2 2.0 REQUIRED)
+
+add_executable(cgvm_vnc src/main.c)
+set_target_properties(cgvm_vnc PROPERTIES
+  RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+target_link_libraries(cgvm_vnc LibVNCServer::vncclient SDL2::SDL2)

vnc-client/src/main.c

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+#include <SDL2/SDL.h>
+#include <rfb/rfbclient.h>
+#include <stdio.h>
+#include <signal.h>
+#include <assert.h>
+
+/* Application globals */
+struct app {
+    rfbClient *client;
+    SDL_Window *window;
+    SDL_Surface *surface;
+};
+static struct app app = { 0 };
+
+static void cleanup(void)
+{
+    if(app.client)
+        rfbClientCleanup(app.client);
+    if(app.window)
+        SDL_DestroyWindow(app.window);
+    SDL_Quit();
+}
+
+static void fb_update(rfbClient *client)
+{
+/*    SDL_LockSurface(app.surface);
+    assert(app.surface->format->BytesPerPixel == 4);
+    uint8_t *buffer = (void *)app.surface->pixels;
+    for(int y = 0; y < app.surface->h; y++) {
+        for(int x = 0; x < app.surface->w; x++) {
+            int offset = y * app.surface->pitch + 4 * x;
+            // R, G, B
+            buffer[offset + 2] = 255;
+            buffer[offset + 1] = 255;
+            buffer[offset + 0] = 0;
+        }
+    }
+    SDL_UnlockSurface(app.surface); */
+    SDL_UpdateWindowSurface(app.window);
+}
+
+int main(void)
+{
+    SDL_Init(SDL_INIT_VIDEO);
+    atexit(cleanup);
+    signal(SIGINT, exit);
+
+    app.window = SDL_CreateWindow("CG Virtual Monitor test VNC client",
+        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 396, 224, 0);
+    app.surface = SDL_GetWindowSurface(app.window);
+
+    app.client = rfbGetClient(8, 3, 4);
+    app.client->FinishedFrameBufferUpdate = fb_update;
+    app.client->width = 396;
+    app.client->height = 224;
+    app.client->frameBuffer = app.surface->pixels;
+
+    app.client->format.bitsPerPixel=32;
+    app.client->format.redShift=app.surface->format->Rshift;
+    app.client->format.greenShift=app.surface->format->Gshift;
+    app.client->format.blueShift=app.surface->format->Bshift;
+    app.client->format.redMax=app.surface->format->Rmask>>app.client->format.redShift;
+    app.client->format.greenMax=app.surface->format->Gmask>>app.client->format.greenShift;
+    app.client->format.blueMax=app.surface->format->Bmask>>app.client->format.blueShift;
+    SetFormatAndEncodings(app.client);
+
+    int argc = 4;
+    char *argv[] = { "cgvm_vnc", "-encodings", "raw", "127.0.0.1", NULL };
+    if(!rfbInitClient(app.client, &argc, argv)) {
+        fprintf(stderr, "rfbInitClient failed\n");
+        app.client = NULL;
+        return 1;
+    }
+
+    while(1) {
+        SDL_Event e;
+        while(SDL_PollEvent(&e)) {
+            if(e.type == SDL_QUIT) {
+                fprintf(stderr, "SDL_QUIT: Exiting...\n");
+                exit(0);
+            }
+        }
+
+        int i = WaitForMessage(app.client, 100);
+        if(i < 0) {
+            fprintf(stderr, "WaitForMessage() select: %d\n", i);
+            continue;
+        }
+        else if(i > 0 && !HandleRFBServerMessage(app.client)) {
+            fprintf(stderr, "HandleRFBServerMessage() failed\n");
+            continue;
+        }
+    }
+
+    return 0;
+}