Re: [PATCH v6 2/4] drm/rect: Add drm_rect_overlap()

[Jocelyn Falempe <jfalempe@redhat.com>]

On 12/08/2024 15:49, Jani Nikula wrote:
> On Mon, 12 Aug 2024, Jocelyn Falempe <jfalempe@redhat.com> wrote:
>> Check if two rectangles overlap.
>> It's a bit similar to drm_rect_intersect() but this won't modify
>> the rectangle.
>> Simplifies a bit drm_panic.
> 
> Based on the name, I'd expect drm_rect_overlap() to return true for
> *any* overlap, while this one seems to mean if one rectangle is
> completely within another, with no adjacent borders.

It's what I intended, but I may have messed up the formula.
> 
> I'd expect a drm_rect_overlap() to return true for this:
> 
>   +-------+
>   |   +---+---+
>   |   |       |
>   +---+       |
>       |       |
>       +-------+

if r1 is the top left rectangle, you've got:

r1->x2 > r2->x1   => true
r2->x2 > r1->x1   => true
r1->y2 > r2->y1   => true
r2->y2 > r1->y1   => true

So they count as overlap.

Checking in stackoverflow, they use the same formula:
https://stackoverflow.com/questions/306316/determine-if-two-rectangles-overlap-each-other

> 
> While this seems to be required instead:
> 
>   +-------+
>   | +---+ |
>   | |   | |
>   | +---+ |
>   +-------+
> 
> 
> IOW, I find the name misleading.
> 
> BR,
> Jani.
> 
> 
>>
>> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
>> ---
>>   drivers/gpu/drm/drm_panic.c |  3 +--
>>   include/drm/drm_rect.h      | 15 +++++++++++++++
>>   2 files changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
>> index 0a047152f88b8..59fba23e5fd7a 100644
>> --- a/drivers/gpu/drm/drm_panic.c
>> +++ b/drivers/gpu/drm/drm_panic.c
>> @@ -529,8 +529,7 @@ static void draw_panic_static_user(struct drm_scanout_buffer *sb)
>>   	/* Fill with the background color, and draw text on top */
>>   	drm_panic_fill(sb, &r_screen, bg_color);
>>   
>> -	if ((r_msg.x1 >= logo_width || r_msg.y1 >= logo_height) &&
>> -	    logo_width <= sb->width && logo_height <= sb->height) {
>> +	if (!drm_rect_overlap(&r_logo, &r_msg)) {
>>   		if (logo_mono)
>>   			drm_panic_blit(sb, &r_logo, logo_mono->data, DIV_ROUND_UP(logo_width, 8),
>>   				       fg_color);
>> diff --git a/include/drm/drm_rect.h b/include/drm/drm_rect.h
>> index 73fcb899a01da..7bafde747d560 100644
>> --- a/include/drm/drm_rect.h
>> +++ b/include/drm/drm_rect.h
>> @@ -238,6 +238,21 @@ static inline void drm_rect_fp_to_int(struct drm_rect *dst,
>>   		      drm_rect_height(src) >> 16);
>>   }
>>   
>> +/**
>> + * drm_rect_overlap - Check if two rectangles overlap
>> + * @r1: first rectangle
>> + * @r2: second rectangle
>> + *
>> + * RETURNS:
>> + * %true if the rectangles overlap, %false otherwise.
>> + */
>> +static inline bool drm_rect_overlap(const struct drm_rect *r1,
>> +				    const struct drm_rect *r2)
>> +{
>> +	return (r1->x2 > r2->x1 && r2->x2 > r1->x1 &&
>> +		r1->y2 > r2->y1 && r2->y2 > r1->y1);
>> +}
>> +
>>   bool drm_rect_intersect(struct drm_rect *r, const struct drm_rect *clip);
>>   bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
>>   			  const struct drm_rect *clip);
>