select_area.c

#include <gtk/gtk.h>
#include "vdcapp.h"

static gboolean select_window_button_press(GtkWidget *window,
                                           GdkEventButton *event,
                                           struct select_data *select_data) {
    if(select_data->started) {
        return TRUE;
    }

    select_data->started = TRUE;
    select_data->rect.x = event->x_root;
    select_data->rect.y = event->y_root;

    return TRUE;
}

static gboolean select_window_button_release(GtkWidget *window,
                                             GdkEventButton *event,
                                             struct select_data *select_data) {
    if(!select_data->started) {
        return TRUE;
    }

    select_data->rect = (GdkRectangle) {
            .x = MIN(select_data->rect.x, event->x_root),
            .y = MIN(select_data->rect.y, event->y_root),
            .width = ABS(select_data->rect.x - event->x_root),
            .height = ABS(select_data->rect.y - event->y_root)
    };

    // TODO: handle height/width of 0
    gtk_main_quit();

    return TRUE;
}

static gboolean select_window_motion_notify(GtkWidget *window,
                                            GdkEventMotion *event,
                                            struct select_data *select_data) {
    GdkRectangle rect;

    if(!select_data->started) {
        return TRUE;
    }

    rect = (GdkRectangle) {
            .x = MIN(select_data->rect.x, event->x_root),
            .y = MIN(select_data->rect.y, event->y_root),
            .width = ABS(select_data->rect.x - event->x_root),
            .height = ABS(select_data->rect.y - event->y_root)
    };

    // TODO: handle width, height <= 0 like in gnome-screenshot?

    gtk_window_move(GTK_WINDOW(window), rect.x, rect.y);
    gtk_window_resize(GTK_WINDOW(window), rect.width, rect.height);

    // TODO: app-paintable stuff?
}

static gboolean select_window_draw(GtkWidget *window,
                                   cairo_t *cr,
                                   gpointer unused) {
    GtkStyleContext *style;

    style = gtk_widget_get_style_context(window);

    if(gtk_widget_get_app_paintable(window)) {
        cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
        cairo_set_source_rgba(cr, 0, 0, 0, 0);

        cairo_paint(cr);

        gtk_style_context_save(style);
        gtk_style_context_add_class(style, GTK_STYLE_CLASS_RUBBERBAND);

        gtk_render_background(style, cr, 0, 0,
                              gtk_widget_get_allocated_width(window),
                              gtk_widget_get_allocated_height(window));

        gtk_style_context_restore(style);
    }

    return TRUE;
}

// guided by https://gitlab.gnome.org/GNOME/gnome-screenshot project
// screen-shot-area-selection.c file
void select_area(struct select_data *select_data) {
    GtkWidget *window;
    GdkScreen *screen;
    GdkVisual *visual;
    GdkDisplay *display;
    GdkCursor *cursor;
    GdkDeviceManager *manager;
    GdkDevice *pointer;
    GdkGrabStatus grab_status;

    // now for testing TODO: later change to other, non-arbitrary values
    select_data->rect = (GdkRectangle) {
        .x = 100,
        .y = 100,
        .width = 100,
        .height = 100
    };
    select_data->started = FALSE;

    screen = gdk_screen_get_default();
    visual = gdk_screen_get_rgba_visual(screen);
    select_data->screen = (GdkRectangle) {
        .x = 0,
        .y = 0,
        .width = gdk_screen_get_width(screen),
        .height = gdk_screen_get_height(screen),
    };

    window = gtk_window_new(GTK_WINDOW_POPUP);
    select_data->window = window;
    if(gdk_screen_is_composited(screen) && visual) {
        gtk_widget_set_visual(window, visual);
        gtk_widget_set_app_paintable(window, TRUE);
    }

    g_signal_connect(window, "draw", G_CALLBACK(select_window_draw), NULL);
    g_signal_connect(window, "motion-notify-event",
                     G_CALLBACK(select_window_motion_notify), select_data);
    g_signal_connect(window, "button-press-event",
                     G_CALLBACK(select_window_button_press), select_data);
    g_signal_connect(window, "button-release-event",
                     G_CALLBACK(select_window_button_release), select_data);

    // TODO: change to other, non-arbitrary values
    gtk_window_move(GTK_WINDOW(window), 100, 100);
    gtk_window_resize(GTK_WINDOW(window), 100, 100);
    gtk_widget_show(window);

    // grab pointer
    display = gtk_widget_get_display(select_data->window);
    cursor = gdk_cursor_new_for_display(display, GDK_CROSSHAIR);
    manager = gdk_display_get_device_manager(display);
    pointer = gdk_device_manager_get_client_pointer(manager);

    grab_status = gdk_device_grab(pointer,
                                  gtk_widget_get_window(select_data->window),
                                  GDK_OWNERSHIP_NONE, FALSE,
                                  GDK_POINTER_MOTION_MASK | GDK_BUTTON_PRESS_MASK
                                  | GDK_BUTTON_RELEASE_MASK,
                                  cursor, GDK_CURRENT_TIME);

    if(grab_status != GDK_GRAB_SUCCESS) {
        g_object_unref(cursor);
        g_print("gdk grab failure");
        // TODO: abort
        return;
    }

    // don't need to grab keyboard as well

    gtk_main();

    gdk_device_ungrab(pointer, GDK_CURRENT_TIME);
    gtk_widget_destroy(select_data->window);
    g_object_unref(cursor);
    gdk_flush();
}