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Work around for multiple displays with respective scales #245

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Work around for multiple displays with respective scales #245

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48e10b9
Work around for multiple displays with respective scales
wsxyeah Aug 26, 2018
8313e60
Extract out logical size update operation into screen.c
wsxyeah Sep 5, 2018
a5e690d
Turn scale factor into float for better precision
wsxyeah Sep 5, 2018
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11 changes: 11 additions & 0 deletions app/src/scrcpy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,17 @@ static SDL_bool event_loop(void) {
case SDL_WINDOWEVENT_EXPOSED:
case SDL_WINDOWEVENT_SIZE_CHANGED:
screen_render(&screen);
int scale_x, scale_y;
get_window_scale(SDL_GetWindowFromID(event.button.windowID), &scale_x, &scale_y);
if (scale_x != screen.scale_x || scale_y != screen.scale_y) {
int logical_width, logical_height;
SDL_RenderGetLogicalSize(screen.renderer, &logical_width, &logical_height);
logical_width *= (float)scale_x / screen.scale_x;
logical_height *= (float)scale_y / screen.scale_y;
screen.scale_x = scale_x;
screen.scale_y = scale_y;
SDL_RenderSetLogicalSize(screen.renderer, logical_width, logical_height);
}
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The computing should be done in screen.c.

Typically, add a set_logical_size() wrapper for this call and this one.

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Oh, but I'm stupid, you need it there so that it changes when you moves the window from/to the secondary screen (it still needs be done in screen.c though).

break;
}
break;
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10 changes: 10 additions & 0 deletions app/src/screen.c
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Expand Up @@ -65,6 +65,15 @@ static void set_window_size(struct screen *screen, struct size new_size) {
}
}

void get_window_scale(SDL_Window *window, int *scale_x, int *scale_y) {
int win_w, win_h;
SDL_GetWindowSize(window, &win_w, &win_h);
int output_w, output_h;
SDL_GL_GetDrawableSize(window, &output_w, &output_h);
*scale_x = output_w / win_w;
*scale_y = output_h / win_h;
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This loses precision if the scale is not an integer.

}

// get the preferred display bounds (i.e. the screen bounds with some margins)
static SDL_bool get_preferred_display_bounds(struct size *bounds) {
SDL_Rect rect;
Expand Down Expand Up @@ -168,6 +177,7 @@ SDL_bool screen_init_rendering(struct screen *screen, const char *device_name, s
screen_destroy(screen);
return SDL_FALSE;
}
get_window_scale(screen->window, &screen->scale_x, &screen->scale_y);

SDL_Surface *icon = read_xpm(icon_xpm);
if (!icon) {
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4 changes: 4 additions & 0 deletions app/src/screen.h
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Expand Up @@ -12,6 +12,8 @@ struct screen {
SDL_Renderer *renderer;
SDL_Texture *texture;
struct size frame_size;
int scale_x;
int scale_y;
//used only in fullscreen mode to know the windowed window size
struct size windowed_window_size;
SDL_bool has_frame;
Expand Down Expand Up @@ -66,4 +68,6 @@ void screen_resize_to_fit(struct screen *screen);
// resize window to 1:1 (pixel-perfect)
void screen_resize_to_pixel_perfect(struct screen *screen);

void get_window_scale(SDL_Window *window, int *scale_x, int *scale_y);
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The scale is not necessary an integer.

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I don't get any non-integral scale display device for now 😅.
So I will just turn the variables into float, but some tests on such devices are still necessary.

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@rom1v rom1v Sep 5, 2018 •
edited
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There is no need to use floating point values here (the ratio will lose precision), you can use a "rational" instead (cf here)

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Do you mean use rational to denote the scale factor?
But we still have to convert it to float when performing the new logical size scale calculation.

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@rom1v rom1v Sep 6, 2018 •
edited
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But we still have to convert it to float when performing the new logical size scale calculation.

No, we don't: the width and height fit into 16 bits, so using 32 bits, you can get the best possible precision using only integers:
2f6db25#diff-cbb13e05de08766971505804dff53448R139


#endif