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vwebp: handle window resizing properly

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The image is scaled to fit the whole viewport.
Avoid some oddities with offsets, etc.

removes some TODO.

Change-Id: I52fae9ca80a2feed234f32261c7f6358d7594e21
This commit is contained in:
Pascal Massimino 2016-09-29 07:30:03 +02:00
parent f79450ca02
commit 9310d19258
1 changed files with 12 additions and 6 deletions
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18
examples/vwebp.c
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@ -64,6 +64,7 @@ static struct {
WebPIterator curr_frame;
WebPIterator prev_frame;
WebPChunkIterator iccp;
int viewport_width, viewport_height;
} kParams;
static void ClearPreviousPic(void) {
@ -251,13 +252,15 @@ static void HandleKey(unsigned char key, int pos_x, int pos_y) {
}
static void HandleReshape(int width, int height) {
// TODO(skal): proper handling of resize, esp. for large pictures.
// + key control of the zoom.
// TODO(skal): should we preserve aspect ratio?
// Also: handle larger-than-screen pictures correctly.
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
kParams.viewport_width = width;
kParams.viewport_height = height;
}
static void PrintString(const char* const text) {
@ -299,7 +302,8 @@ static void HandleDisplay(void) {
GLfloat xoff, yoff;
if (pic == NULL) return;
glPushMatrix();
glPixelZoom(1, -1);
glPixelZoom((GLfloat)(+1. / kParams.canvas_width * kParams.viewport_width),
(GLfloat)(-1. / kParams.canvas_height * kParams.viewport_height));
xoff = (GLfloat)(2. * curr->x_offset / kParams.canvas_width);
yoff = (GLfloat)(2. * curr->y_offset / kParams.canvas_height);
glRasterPos2f(-1.f + xoff, 1.f - yoff);
@ -308,8 +312,6 @@ static void HandleDisplay(void) {
if (prev->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND ||
curr->blend_method == WEBP_MUX_NO_BLEND) {
// TODO(later): these offsets and those above should factor in window size.
// they will be incorrect if the window is resized.
// glScissor() takes window coordinates (0,0 at bottom left).
int window_x, window_y;
int frame_w, frame_h;
@ -329,6 +331,10 @@ static void HandleDisplay(void) {
}
glEnable(GL_SCISSOR_TEST);
// Only update the requested area, not the whole canvas.
window_x = window_x * kParams.viewport_width / kParams.canvas_width;
window_y = window_y * kParams.viewport_height / kParams.canvas_height;
frame_w = frame_w * kParams.viewport_width / kParams.canvas_width;
frame_h = frame_h * kParams.viewport_height / kParams.canvas_height;
glScissor(window_x, window_y, frame_w, frame_h);
glClear(GL_COLOR_BUFFER_BIT); // use clear color
@ -371,6 +377,7 @@ static void StartDisplay(void) {
glutInitWindowSize(width, height);
glutCreateWindow("WebP viewer");
glutDisplayFunc(HandleDisplay);
glutReshapeFunc(HandleReshape);
glutIdleFunc(NULL);
glutKeyboardFunc(HandleKey);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@ -379,7 +386,6 @@ static void StartDisplay(void) {
GetColorf(kParams.bg_color, 8),
GetColorf(kParams.bg_color, 16),
GetColorf(kParams.bg_color, 24));
HandleReshape(width, height);
glClear(GL_COLOR_BUFFER_BIT);
DrawCheckerBoard();
}