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[英]How to get GTK Cairo to plot multiple times without a triggering event
[英]How to accelerate the Cairo painting speed of Gtk2+ on Arm without a GPU
我正在具有A53(1.5GHz)CPU但在Linux上不支持GPU的手臂设备上运行Gtk2 +(配置有DirectFB,没有X系统)。 它有一个大小为:3840 * 2160的帧缓冲区。 现在,我需要在屏幕上画一些线,圆...就像Windows画板一样。 因此,我尝试用开罗做它,但是我发现开罗绘画的速度太慢了! 从左上方到右下方绘制一条线需要400毫秒! 因为鼠标如此快速地移动,并且在每个运动事件处,我都需要更新整个屏幕并重新绘制线条,但是绘制时间太长,因此运动事件的响应太慢。 我不知道是否有某种方法可以加快速度,以使绘图任务像MS Paint一样流畅。 我也尝试过gdk_draw_line,但是更新也花费了太长时间...下面是一些代码:
#include <gtk/gtk.h>
#include <time.h>
static gint prex, prey, nowx, nowy;
static GtkWidget *window = NULL;
static gboolean on_button_press_event(GtkWidget *widget, GdkEventButton *event, gpointer data)
{
if (event->button == 1) {
prex = event->x;
prey = event->y;
}
return TRUE;
}
static gboolean on_button_release_event(GtkWidget *widget, GdkEventButton *event, gpointer data)
{
if (event->button == 1) {
prex = 0;
prey = 0;
}
return TRUE;
}
static gboolean on_motion_notify_event(GtkWidget *widget, GdkEventMotion *event, gpointer data)
{
GdkModifierType state;
int minx, miny, maxx, maxy;
GdkRectangle update_rect;
gdk_window_get_pointer(event->window, &nowx, &nowy, &state);
if (state & GDK_BUTTON1_MASK) {
if (prex != 0 && prey != 0) {
minx = prex < nowx ? prex : nowx;
miny = prey < nowy ? prey : nowy;
maxx = prex < nowx ? nowx : prex;
maxy = prey < nowy ? nowy : prey;
update_rect.x = minx;
update_rect.y = miny;
update_rect.width = maxx - minx;
update_rect.height = maxy - miny;
gdk_window_invalidate_rect(widget->window, &update_rect, FALSE);
}
}
return TRUE;
}
void on_expose_event(GtkWidget *widget, GdkEventMotion *event, gpointer data)
{
struct timeval tv_start, tv_end;
cairo_t *cr;
cr = gdk_cairo_create(widget->window);
cairo_set_source_rgb(cr, 0, 0, 0);
cairo_set_line_width(cr, 1);
cairo_move_to(cr, prex, prey);
cairo_line_to(cr, nowx, nowy);
gettimeofday(&tv_start, NULL);
cairo_stroke(cr);
gettimeofday(&tv_end, NULL);
printf("draw use time: %dus\n", (tv_end.tv_sec-tv_start.tv_sec)*1000000 + (tv_end.tv_usec-tv_start.tv_usec));
//this takes almost 400ms when I draw a line from the upper left to lower right.
cairo_destroy(cr);
return FALSE;
}
int main (int argc,char* argv[])
{
GtkWidget *canvas;
gtk_init(&argc,&argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_default_size(GTK_WINDOW(window), 3840, 2160);
g_signal_connect(G_OBJECT(window), "delete_event", G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);
canvas = gtk_drawing_area_new();
gtk_widget_set_size_request(canvas, 3840, 2160);
gtk_container_add(GTK_CONTAINER(window), canvas);
g_signal_connect(canvas, "expose_event", G_CALLBACK(on_expose_event), NULL);
g_signal_connect(canvas, "motion_notify_event", G_CALLBACK(on_motion_notify_event), NULL);
g_signal_connect(canvas, "button_press_event", G_CALLBACK(on_button_press_event), NULL);
g_signal_connect(canvas, "button_release_event", G_CALLBACK(on_button_release_event), NULL);
gtk_widget_set_events(canvas, gtk_widget_get_events(canvas)
| GDK_LEAVE_NOTIFY_MASK | GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK
| GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK);
gtk_widget_show_all(window);
gtk_main();
return FALSE;
}
仅在最后一次鼠标移动事件超过KL毫秒但不超过MN毫秒(当然,KL <MN)时,才尝试重画线。 这样,您可以减少计算需求,同时仍然提供响应能力。
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