Getting Started
Well, we've got to start somewhere. Personally, I don't like starting with Hello World. Generally doesn't give a good feel for the toolkit. So, we're going to start with something a bit more complicated. We're going to make a simple image preview application.Ok, we're going to jump straight into the action here. There is a complete code listing provided at the end of the article.
#include <Ewl.h> #include <Ecore_File.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #ifndef PATH_MAX #define PATH_MAX 4096 #endif static void usage(void); static void build_gui(const char *dir); static void cb_main_quit(Ewl_Widget *w, void *ev, void *data);
Every Ewl application has to include Ewl.h. This will provide all the necessary headers in order to work with Ewl. Along with this we include a few other common headers. The Ecore_File.h header will provide us with some routines to work with files and directories.
- Note:
- All Ewl callbacks use the same signature. void name(Ewl_Widget *w, void *ev, void *data). This makes life a lot easier when working with Ewl as you don't have to go looking up what the specific signature of your callback.
int main(int argc, char ** argv) { int ret = 1, i; char *dir = NULL; if (!ewl_init(&argc, argv)) { fprintf(stderr, "Unable to initialize Ewl.\n"); goto EXIT; } for (i = 1; i < argc; i++) { if (!strncmp(argv[i], "-h", 2)) { usage(); ret = 0; goto EWL_SHUTDOWN; } else if (!strncmp(argv[i], "-d", 2)) { if (++i < argc) dir = strdup(argv[i]); else { usage(); goto EWL_SHUTDOWN; } } } if (!dir) { dir = getenv("PWD"); if (!dir) { fprintf(stderr, "Unable to find directory for images.\n"); goto EWL_SHUTDOWN; } else dir = strdup(dir); } if (!ecore_file_exists(dir) || !ecore_file_is_dir(dir)) { fprintf(stderr, "Invalid directory given.\n"); goto DIR_SHUTDOWN; } build_gui(dir); ewl_main(); ret = 0; DIR_SHUTDOWN: free(dir); EWL_SHUTDOWN: ewl_shutdown(); EXIT: return ret; }
Moving on we get to the main routine for the application. The things to note in here are the use of ewl_init() to initialize Ewl. This will return FALSE if the library was unable to be initailized, TRUE is returned otherwise. Passing in argc and argv is optional. If you set them to NULL Ewl won't be able to parse out any of its command line flags but will work correctly otherwise.
With Ewl initialized we then proceed to do a bit of work to parse out our command line options and verifying that the given directory exists. With this done we call build_gui(const char *dir) to build the interface. We'll get to that in a minute.
In order for your Ewl application to run you have to call ewl_main(). This will start the main loop running. This loop will only exit when the application is terminated. The ewl_main() call will actually call ewl_shutdown() before it exists. I add one in anyway in case we've terminated before running the main loop. Just makes sure we always clean up after ourselves.
static void usage(void) { printf("image_preview [OPTIONS]\n" " OPTIONS\n" " -d <dir> - Directory of images.\n" " -h - Show help.\n" "\n"); }
This is just a simple routine to spit out the usage information for the app. Nothing to see here, moving along.
static void build_gui(const char *dir) { Ewl_Widget *win, *box, *scroll, *o; Ecore_List *files; char *file; win = ewl_window_new(); ewl_window_name_set(EWL_WINDOW(win), "image_preview"); ewl_window_title_set(EWL_WINDOW(win), "Image Preview"); ewl_window_class_set(EWL_WINDOW(win), "image_preview"); ewl_object_size_request(EWL_OBJECT(win), 600, 400); ewl_callback_append(win, EWL_CALLBACK_DELETE_WINDOW, cb_main_quit, NULL); ewl_widget_show(win);
The first thing we need to do is create the window. This is done with a simple call to ewl_window_new(). We can then proceed to set the name, class and title of the window. These are things the window manager will use and should typically always be set. We then want to force our window to be a specific size. Ewl can determine this size for you at runtime but if you force a size by using the ewl_object_size_request() call. You'll notice we're casting our window to an Ewl_Object * structure. This is because Ewl_Window inherits from Ewl_Object.
- Note:
- All of the _new() routines in Ewl return the same Ewl_Widget * object. Ewl uses a form of inheritance for it's objects. Take a look at the Object Model section for more information
- Note:
- By default an Ewl_Window doesn't have a layout policy. Any widgets that are packed into the window will be placed at 0,0 (the top left of the screen). In order to get an acceptable layout you pretty much always need to pack one of the container widgets into the window.
scroll = ewl_scrollpane_new(); ewl_container_child_append(EWL_CONTAINER(win), scroll); ewl_widget_show(scroll);
If we have a lot of images in our directory we'll want to be able to scroll through them. This is easily done by creating a scrollpane. Similar to the window we use ewl_scrollpane_new() to create the new scrollpane. We then pack the pane into the window.
- Note:
- More information on widget packing can be found in the Widget Packing section.
box = ewl_hfreebox_new(); ewl_container_child_append(EWL_CONTAINER(scroll), box); ewl_widget_show(box);
The freebox in Ewl provides a nice autolayout of widgets that will shift with the window size. In this case we want the icons to layout in a horizontal fashion so we call ewl_hfreebox_new(). If we had wanted a vertical layout we would have used ewl_vfreebox_new(). We then pack the freebox into the scrollpane.
files = ecore_file_ls(dir);
ecore_list_goto_first(files);
while ((file = ecore_list_next(files)))
{
const char *mime;
char path[PATH_MAX];
snprintf(path, sizeof(path), "%s/%s", dir, file);
mime = ewl_io_manager_uri_mime_type_get(path);
if (!mime || strncmp(mime, "image/", 6))
continue;
o = ewl_icon_simple_new();
ewl_icon_thumbnailing_set(EWL_ICON(o), TRUE);
ewl_icon_label_set(EWL_ICON(o), file);
ewl_icon_image_set(EWL_ICON(o), path, NULL);
ewl_icon_constrain_set(EWL_ICON(o), 128);
ewl_container_child_append(EWL_CONTAINER(box), o);
ewl_widget_show(o);
}
ecore_list_destroy(files);
}
We now get into the meat of the application. We get a listing of files in the given directory using ecore_file_list() and iterate the returned files. We only really care about images so we use the ewl_io_manager_uri_mime_type_get() call to get the MIME type of our file.
For each image we then proceed to get an Ewl_Icon. This is done with ewl_icon_simple_new(). We're using the simple version of Ewl_Icon as we don't need many of the provided features. The one we do need, that simple disables, is thumbnailing. To that end we re-enable the thumbing by calling ewl_icon_thumbnailling_set().
We want to set the label for our icon to the name of the given file so we call ewl_icon_label_set() and set the actual image into the icon using ewl_icon_image_set(). You'll only need to use the path option if you're setting an Edje as the image. We aren't in this case so we set it to NULL.
We want our image to be 128 pixels in size so we call ewl_icon_image_constrain() to force the size to 128 pixels.
- Note:
- As the images are thumbnailed Ewl will set a temporary image to be displayed. You could also set an alternate text string to be displayed in case the image isn't available throught the Ewl_Icon API. The thumbnailling is done with Epsilon and follows the FreeDesktop specification for image thumbnailling.
static void cb_main_quit(Ewl_Widget *win, void *ev, void *data) { ewl_main_quit(); }
The cb_main_quit() routine will be trigged when the window receives a close event. We terminate the main loop by calling ewl_main_quit() which will cause the application to exit the ewl_main() loop started in the main routine.
Compilation
With the code written it's a simple process to get everything compiled. We can use pkg-config to get the information on the CFLAGS and LDLIBS needed to successfully compile an Ewl application.
gcc -g -o image_preview image_preview.c `pkg-config ewl --libs --cflags` -lecore_file
Code Listing
#include <Ewl.h> #include <Ecore_File.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #ifndef PATH_MAX #define PATH_MAX 4096 #endif static void usage(void); static void build_gui(const char *dir); static void cb_main_quit(Ewl_Widget *w, void *ev, void *data); int main(int argc, char ** argv) { int ret = 1, i; char *dir = NULL; if (!ewl_init(&argc, argv)) { fprintf(stderr, "Unable to initialize Ewl.\n"); goto EXIT; } for (i = 1; i < argc; i++) { if (!strncmp(argv[i], "-h", 2)) { usage(); ret = 0; goto EWL_SHUTDOWN; } else if (!strncmp(argv[i], "-d", 2)) { if (++i < argc) dir = strdup(argv[i]); else { usage(); goto EWL_SHUTDOWN; } } } if (!dir) { dir = getenv("PWD"); if (!dir) { fprintf(stderr, "Unable to find directory for images.\n"); goto EWL_SHUTDOWN; } else dir = strdup(dir); } if (!ecore_file_exists(dir) || !ecore_file_is_dir(dir)) { fprintf(stderr, "Invalid directory given.\n"); goto DIR_SHUTDOWN; } build_gui(dir); ewl_main(); ret = 0; DIR_SHUTDOWN: free(dir); EWL_SHUTDOWN: ewl_shutdown(); EXIT: return ret; } static void usage(void) { printf("image_preview [OPTIONS]\n" " OPTIONS\n" " -d <dir> - Directory of images.\n" " -h - Show help.\n" "\n"); } static void build_gui(const char *dir) { Ewl_Widget *win, *box, *scroll, *o; Ecore_List *files; char *file; win = ewl_window_new(); ewl_window_name_set(EWL_WINDOW(win), "image_preview"); ewl_window_title_set(EWL_WINDOW(win), "Image Preview"); ewl_window_class_set(EWL_WINDOW(win), "image_preview"); ewl_object_size_request(EWL_OBJECT(win), 600, 400); ewl_callback_append(win, EWL_CALLBACK_DELETE_WINDOW, cb_main_quit, NULL); ewl_widget_show(win); scroll = ewl_scrollpane_new(); ewl_container_child_append(EWL_CONTAINER(win), scroll); ewl_widget_show(scroll); box = ewl_hfreebox_new(); ewl_container_child_append(EWL_CONTAINER(scroll), box); ewl_widget_show(box); files = ecore_file_ls(dir); ecore_list_goto_first(files); while ((file = ecore_list_next(files))) { const char *mime; char path[PATH_MAX]; snprintf(path, sizeof(path), "%s/%s", dir, file); mime = ewl_io_manager_uri_mime_type_get(path); if (!mime || strncmp(mime, "image/", 6)) continue; o = ewl_icon_simple_new(); ewl_icon_thumbnailing_set(EWL_ICON(o), TRUE); ewl_icon_label_set(EWL_ICON(o), file); ewl_icon_image_set(EWL_ICON(o), path, NULL); ewl_icon_constrain_set(EWL_ICON(o), 128); ewl_container_child_append(EWL_CONTAINER(box), o); ewl_widget_show(o); } ecore_list_destroy(files); } static void cb_main_quit(Ewl_Widget *w, void *ev, void *data) { ewl_main_quit(); }