feat(application): allow print surface to stdout

This allows a user to output the final surface to `stdout` using:

- `-O`
- `--print-stdout`

Also adding another keybinding to exit the application `Ctrl+w` which is
pretty standard.

Closes #2

.vscode/launch.json

@@ -52,6 +52,30 @@
         }
       ]
     },
+    {
+      "name": "swappy - file & stdout",
+      "type": "cppdbg",
+      "request": "launch",
+      "program": "${workspaceFolder}/build/swappy",
+      "args": ["-f", "docs/images/screenshot.png", "-O"],
+      "stopAtEntry": false,
+      "cwd": "${workspaceFolder}",
+      "environment": [
+        {
+          "name": "G_MESSAGES_DEBUG",
+          "value": "all"
+        }
+      ],
+      "externalConsole": false,
+      "MIMode": "gdb",
+      "setupCommands": [
+        {
+          "description": "Enable pretty-printing for gdb",
+          "text": "-enable-pretty-printing",
+          "ignoreFailures": true
+        }
+      ]
+    },
     {
       "name": "swappy - stdin",
       "type": "cppdbg",

README.md

@@ -36,6 +36,12 @@ Select a region and swappshot it:
 swappy -g "$(slurp)"
 ```
 
+Print final surface to stdout (useful to pipe with other tools):
+
+```sh
+grim -g "$(slurp)" - | swappy -O -f - | pngquant -
+```
+
 Grab a swappshot from a specific window under Sway, using `swaymsg` and `jq`:
 
 ```sh
@@ -92,7 +98,7 @@ The following lines can be used as swappy's default:
 - `Ctrl+Shift+z` or `Ctrl+y`: Redo
 - `Ctrl+s`: Save to file (see man page)
 - `Ctrl+c`: Copy to clipboard
-- `Escape` or `q`: Quit swappy
+- `Escape` or `q` or `Ctrl+w`: Quit swappy
 
 ## Limitations
 

include/pixbuf.h

@@ -2,4 +2,5 @@
 
 #include "swappy.h"
 
-void pixbuf_save_to_file(struct swappy_state *state);
+void pixbuf_save_to_file(struct swappy_state *state);
+void pixbuf_save_to_stdout(struct swappy_state *state);

include/swappy.h

@@ -191,6 +191,7 @@ struct swappy_state {
   /* Options */
   char *geometry_str;
   char *file_str;
+  gboolean print_stdout;
 
   struct swappy_box *geometry;
 

src/application.c

@@ -187,6 +187,9 @@ void arrow_clicked_handler(GtkWidget *widget, struct swappy_state *state) {
 }
 
 void application_finish(struct swappy_state *state) {
+  if (state->print_stdout) {
+    pixbuf_save_to_stdout(state);
+  }
   paint_free_all(state);
   buffer_free_all(state);
   cairo_surface_destroy(state->cairo_surface);
@@ -230,6 +233,9 @@ void window_keypress_handler(GtkWidget *widget, GdkEventKey *event,
       case GDK_KEY_b:
         action_toggle_painting_pane(state);
         break;
+      case GDK_KEY_w:
+        gtk_main_quit();
+        break;
       case GDK_KEY_z:
         action_undo(state);
         break;
@@ -652,6 +658,13 @@ bool application_init(struct swappy_state *state) {
           .arg_data = &state->file_str,
           .description = "Load a file at a specific path",
       },
+      {
+          .long_name = "print-stdout",
+          .short_name = 'O',
+          .arg = G_OPTION_ARG_NONE,
+          .arg_data = &state->print_stdout,
+          .description = "Print the final surface to stdout when exiting",
+      },
       {NULL}};
 
   state->app = gtk_application_new("me.jtheoof.swappy",

src/pixbuf.c

@@ -1,12 +1,20 @@
 #include "pixbuf.h"
 
+#include <gio/gunixoutputstream.h>
+
 #include "notification.h"
 
-void pixbuf_save_to_file(struct swappy_state *state) {
+static GdkPixbuf *pixbuf_get_from_state(struct swappy_state *state) {
   guint width = gtk_widget_get_allocated_width(state->ui->area);
   guint height = gtk_widget_get_allocated_height(state->ui->area);
   GdkPixbuf *pixbuf =
       gdk_pixbuf_get_from_surface(state->cairo_surface, 0, 0, width, height);
+
+  return pixbuf;
+}
+
+void pixbuf_save_to_file(struct swappy_state *state) {
+  GdkPixbuf *pixbuf = pixbuf_get_from_state(state);
   GError *error = NULL;
 
   time_t current_time;
@@ -34,3 +42,25 @@ void pixbuf_save_to_file(struct swappy_state *state) {
   g_free(message);
   g_object_unref(pixbuf);
 }
+
+void pixbuf_save_to_stdout(struct swappy_state *state) {
+  GdkPixbuf *pixbuf = pixbuf_get_from_state(state);
+  GOutputStream *out;
+  GError *error = NULL;
+
+  out = g_unix_output_stream_new(STDOUT_FILENO, TRUE);
+
+  if (error != NULL) {
+    g_warning("unable to open stdout for readwrite: %s", error->message);
+    g_error_free(error);
+    return;
+  }
+
+  gdk_pixbuf_save_to_stream(pixbuf, out, "png", NULL, &error);
+
+  if (error != NULL) {
+    g_warning("unable to save surface to stdout: %s", error->message);
+    g_error_free(error);
+    return;
+  }
+}

swappy.1.scd

@@ -39,6 +39,10 @@ to: *$HOME/Desktop*.
 	If set to *-*, read the file from standard input instead. This is grim
 	friendly.
 
+*-O*
+	Print the final surface to stdout. This is useful to pipe swappy with other
+	tools (eg: pngquant).
+
 # CONFIG FILE
 
 The config file is located at *$XDG\_CONFIG\_HOME/swappy/config* or at
@@ -93,7 +97,7 @@ The following lines can be used as swappy's default:
 - *Ctrl+Shift+z* or *Ctrl+y*: Redo
 - *Ctrl+s*: Save to file (see man page)
 - *Ctrl+c*: Copy to clipboard
-- *Escape* or *q*: Quit swappy
+- *Escape* or *q* or *Ctrl+w*: Quit swappy
 
 # AUTHORS