Implement get screenshot of selected display for Linux

Makefile

@@ -46,7 +46,7 @@ ifeq ($(detected_OS),Linux)
 	OBJS+= xclip/xclip.o xclip/xclib.o xscreenshot/xscreenshot.o
 	CFLAGS+= -ftree-vrp -Wformat-signedness -Wshift-overflow=2 -Wstringop-overflow=4 -Walloc-zero -Wduplicated-branches -Wduplicated-cond -Wtrampolines -Wjump-misses-init -Wlogical-op -Wvla-larger-than=65536
 	CFLAGS_OPTIM=-Os
-	LDLIBS=-lunistring -lssl -lcrypto -lX11 -lXmu -lpng
+	LDLIBS=-lunistring -lssl -lcrypto -lX11 -lXmu -lxcb -lxcb-randr -lpng
 	LINK_FLAGS_BUILD=-no-pie -Wl,-s,--gc-sections
 else ifeq ($(detected_OS),Windows)
 	OBJS+= utils/win_image.o

main.c

@@ -198,17 +198,15 @@ static inline void _apply_default_conf(void) {
     if (configuration.max_text_length <= 0) configuration.max_text_length = MAX_TEXT_LENGTH;
     if (configuration.max_file_size <= 0) configuration.max_file_size = MAX_FILE_SIZE;
     if (configuration.cut_sent_files < 0) configuration.cut_sent_files = 0;
+    if (configuration.client_selects_display < 0) configuration.client_selects_display = 0;
+    if (configuration.display <= 0) configuration.display = 1;
 #ifdef WEB_ENABLED
     if (configuration.web_port <= 0) configuration.web_port = WEB_PORT;
     if (configuration.web_mode_enabled < 0) configuration.web_mode_enabled = 0;
 #endif
 #ifdef _WIN32
     if (configuration.tray_icon < 0) configuration.tray_icon = 1;
 #endif
-#if defined(_WIN32) || defined(__APPLE__)
-    if (configuration.client_selects_display < 0) configuration.client_selects_display = 0;
-    if (configuration.display <= 0) configuration.display = 1;
-#endif
 }
 
 #ifdef __linux__

utils/config.c

@@ -288,15 +288,13 @@ static void parse_line(char *line, config *cfg) {
         set_int64(value, &(cfg->max_file_size));
     } else if (!strcmp("cut_sent_files", key)) {
         set_is_true(value, &(cfg->cut_sent_files));
-#ifdef _WIN32
-    } else if (!strcmp("tray_icon", key)) {
-        set_is_true(value, &(cfg->tray_icon));
-#endif
-#if defined(_WIN32) || defined(__APPLE__)
     } else if (!strcmp("client_selects_display", key)) {
         set_is_true(value, &(cfg->client_selects_display));
     } else if (!strcmp("display", key)) {
         set_ushort(value, &(cfg->display));
+#ifdef _WIN32
+    } else if (!strcmp("tray_icon", key)) {
+        set_is_true(value, &(cfg->tray_icon));
 #endif
 #ifdef DEBUG_MODE
     } else {
@@ -328,12 +326,10 @@ void parse_conf(config *cfg, const char *file_name) {
     cfg->max_text_length = 0;
     cfg->max_file_size = 0;
     cfg->cut_sent_files = -1;
-#ifdef _WIN32
-    cfg->tray_icon = -1;
-#endif
-#if defined(_WIN32) || defined(__APPLE__)
     cfg->client_selects_display = -1;
     cfg->display = 0;
+#ifdef _WIN32
+    cfg->tray_icon = -1;
 #endif
     if (ipv4_aton(NULL, &(cfg->bind_addr)) != EXIT_SUCCESS) error_exit("Error initializing bind address");
 

utils/config.h

@@ -43,14 +43,12 @@ typedef struct _config {
     uint32_t max_text_length;
     int64_t max_file_size;
     char cut_sent_files;
+    char client_selects_display;
+    unsigned short display;
 
 #ifdef _WIN32
     char tray_icon;
 #endif
-#if defined(_WIN32) || defined(__APPLE__)
-    char client_selects_display;
-    unsigned short display;
-#endif
 } config;
 
 /*

utils/utils.c

@@ -830,7 +830,6 @@ int put_clipboard_text(char *data, size_t len) {
 }
 
 int get_image(char **buf_ptr, size_t *len_ptr, int mode, int disp) {
-    (void)disp;
     *buf_ptr = NULL;
 
     // Try to get copied image unless the mode is screenshot only
@@ -844,8 +843,9 @@ int get_image(char **buf_ptr, size_t *len_ptr, int mode, int disp) {
     *buf_ptr = NULL;
     *len_ptr = 0;
 
+    if (disp <= 0 || !configuration.client_selects_display) disp = (int)configuration.display;
     // Try to get screenshot unless the mode is copied image only
-    if (mode != IMG_COPIED_ONLY && screenshot_util(len_ptr, buf_ptr) == EXIT_SUCCESS &&
+    if (mode != IMG_COPIED_ONLY && screenshot_util(disp, len_ptr, buf_ptr) == EXIT_SUCCESS &&
         *len_ptr > 8) {  // do not change the order
         return EXIT_SUCCESS;
     }

xscreenshot/xscreenshot.c

@@ -12,6 +12,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <utils/utils.h>
+#include <xcb/randr.h>
+#include <xcb/xcb.h>
 #include <xscreenshot/xscreenshot.h>
 
 /* LSBFirst: BGRA -> RGBA */
@@ -102,11 +104,55 @@ static int png_write_buf(XImage *img, char **buf_ptr, size_t *len) {
     return EXIT_SUCCESS;
 }
 
-int screenshot_util(size_t *len, char **buf) {
+int screenshot_util(int display, size_t *len, char **buf) {
+    xcb_connection_t *dsp = xcb_connect(NULL, NULL);
+    if (xcb_connection_has_error(dsp)) {
+        *len = 0;
+        return EXIT_FAILURE;
+    }
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Waggregate-return"
+    xcb_window_t root = xcb_setup_roots_iterator(xcb_get_setup(dsp)).data->root;
+    xcb_randr_get_monitors_cookie_t cookie = xcb_randr_get_monitors(dsp, root, 1);
+#pragma GCC diagnostic pop
+    xcb_randr_get_monitors_reply_t *reply = xcb_randr_get_monitors_reply(dsp, cookie, NULL);
+    int cnt = xcb_randr_get_monitors_monitors_length(reply);
+    if (display > cnt) {
+        free(reply);
+        xcb_disconnect(dsp);
+        *len = 0;
+        return EXIT_FAILURE;
+    }
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Waggregate-return"
+    xcb_randr_monitor_info_iterator_t itr = xcb_randr_get_monitors_monitors_iterator(reply);
+#pragma GCC diagnostic pop
+
+    int x = 0, y = 0;
+    unsigned int width = 0, height = 0;
+    while (itr.rem) {
+        display--;
+        if (display == 0) {
+            xcb_randr_monitor_info_t *info = itr.data;
+            x = info->x;
+            y = info->y;
+            width = info->width;
+            height = info->height;
+            break;
+        }
+        xcb_randr_monitor_info_next(&itr);
+    }
+    free(reply);
+    xcb_disconnect(dsp);
+    if (width == 0 || height == 0) {
+        *len = 0;
+        return EXIT_FAILURE;
+    }
+
     XImage *img;
     Display *dpy;
     Window win;
-    XWindowAttributes attr;
 
     if (!(dpy = XOpenDisplay(NULL))) {
         *len = 0;
@@ -116,9 +162,8 @@ int screenshot_util(size_t *len, char **buf) {
     win = RootWindow(dpy, 0);
 
     XGrabServer(dpy);
-    XGetWindowAttributes(dpy, win, &attr);
 
-    img = XGetImage(dpy, win, 0, 0, (unsigned int)(attr.width), (unsigned int)(attr.height), 0xffffffff, ZPixmap);
+    img = XGetImage(dpy, win, x, y, width, height, AllPlanes, ZPixmap);
 
     XUngrabServer(dpy);
     XCloseDisplay(dpy);

xscreenshot/xscreenshot.h

@@ -10,6 +10,6 @@
  * Returns 0 on success.
  * Returns -1 if an error occured.
  */
-extern int screenshot_util(size_t *len_p, char **buf_p);
+extern int screenshot_util(int display, size_t *len_p, char **buf_p);
 
 #endif  // XSCREENSHOT_XSCREENSHOT_H_