On Thu, Oct 4, 2012 at 1:46 AM, Steffen Gutmann <muib...@yahoo.com> wrote:
> Hi Tristan!
>
>> I suggest you start by filing an enhancement bug against GtkImage for this.
>
> Yes, I can do that. Just to make sure, I file a new bug for component gtk,
> severity set to enhancement, and put somethign like "Size request of
> GtkImage" into the title. Is this correct?
Right, the bug might have to do more with cropping/scaling support in
GtkImage, rather than it's size request.
>
>> If you have a patch to propose, here would be a good place to discuss
>> the proposed new apis.
>
> I might also be able to work on this and provide a patch. Before starting on
> this, how about the following changes:
>
> Regarding size request:
>
> We add a new property of type boolean to GtkImage. If it is set (default),
> the size request for GtkImage will be the size of the underlying image (or
> the pixel-size), i.e. the exact same behaviour as it is now. If it is set to
> FALSE then the minimum size will be (1, 1) and an application can use
> "width-request" and "height-request" for making the widget size larger. I am
> not sure what a good name for this new property would be, but maybe you have
> a suggestion?. Something like "min-size-is-image-size" would probably make
> the property self-explanatory but is obviously too long compared to other
> existing property names. Maybe "full-image" or "image-size-request"?
>
> Regading placement:
>
> In GTK2, GtkImage cropped the image such that only the center is shown, i.e.
> it took off an equal amount of image content on the left and right, and top
> and bottom. It probably just sets the right clipping mask when drawing the
> image for achieving this. We could simply use the same policy, or we modify
> the usage of GtkWidget's "halign" and "valign" properties. Currently the
> docs reads:
>
> "halign" GtkAlign : Read / Write
While it's true that the align properties make no sense when the
widget's natural size is equal to,
or exceeds the widget's allocation; I'm not exactly sure it's a good
idea to use the GtkWidget's
halign/valign properties directly (i.e. it's like hidden candy, people
wont see it evidently in
the docs/headers for GtkImage and so will probably not discover it).
However I do like the idea of GtkAlign properties for that, where FILL
would mean scale
and CENTER/START/END have the obvious clipping behaviors.
It would have to deal well with situations where the user asked the
image to scale (FILL)
horizontally but to clip vertically ;-)
Also, it should have reasonable behaviors defined for the various
configurations of
a GtkImage (i.e, how does GtkIconSize fit into this ? does it make
sense to allow
the image to try loading the given icon at different sizes to satisfy
the allocation ?
naturally the natural size of the image would have to still be determined by the
user specified icon size, in the case that GtkImage be allocated extra space,
should a larger icon size be tried ? and should the image be upscaled as
a fallback or in situations where the source is a GdkPixbuf ?)
If you're serious about working on this, I would open an enhancement bug
and put your ideas there. You'll be sure to receive more feedback if you do
provide a patch with some test cases showing how it works.
Cheers,
-Tristan
>
> How to distribute horizontal space if widget gets extra space, see GtkAlign
>
> enum GtkAlign
> typedef enum { GTK_ALIGN_FILL, GTK_ALIGN_START, GTK_ALIGN_END,
> GTK_ALIGN_CENTER
> } GtkAlign;
>
> Controls how a widget deals with extra space in a single (x or y)
> dimension.
>
> Alignment only matters if the widget receives a "too large" allocation,
> for example if you packed the widget with the "expand" flag inside a GtkBox,
> then the widget might get extra space. If
> you have for example a 16x16 icon inside a 32x32 space, the icon
> could be scaled and stretched, it could be centered, or it could be
> positioned to one side of the space.
>
> Note that in horizontal context GTK_ALIGN_START and GTK_ALIGN_END are
> interpreted relative to text direction.
> GTK_ALIGN_FILL stretch to fill all space if possible, center if no meaningful
> way to stretch
> GTK_ALIGN_START snap to left or top side, leaving space on right or bottom
> GTK_ALIGN_END snap to right or bottom side, leaving space on left or top
> GTK_ALIGN_CENTER center natural width of widget inside the allocation
>
> My suggestion is to make halign and valign also deal with the case where the
> content of the widget is larger than the allocated space. The modified docs
> would then read:
>
> "halign" GtkAlign : Read / Write
>
> How to distribute horizontal space, see GtkAlign
>
> enum GtkAlign
> typedef enum { GTK_ALIGN_FILL, GTK_ALIGN_START, GTK_ALIGN_END,
> GTK_ALIGN_CENTER
> } GtkAlign;
>
> Controls how a widget deals with space in a single (x or y)
> dimension.
>
> Alignment only matters if the widget receives a "too large" or "too small"
> allocation,
> for example if you packed the widget with the "expand" flag inside a GtkBox,
> then the widget might get extra space. If
> you have for example a 16x16 icon inside a 32x32 space, the icon
> could be scaled and stretched, it could be centered, or it could be
> positioned to one side of the space. Likewise, if you have a 100x100 image
> inside a 20x20 space
> then the image could be scaled down, only the center part of the image be
> shown, or it could
> be cropped to the top left or bottom right part.
>
>
> Note that in horizontal context GTK_ALIGN_START and GTK_ALIGN_END are
> interpreted relative to text direction.
> GTK_ALIGN_FILL stretch or shrink to fill all space if possible, or center if
> no meaningful way to scale
> GTK_ALIGN_START snap to left or top side, leaving space or cropping widget
> content on right or bottom
> GTK_ALIGN_END snap to right or bottom side, leaving space or cropping widget
> content on left or top
> GTK_ALIGN_CENTER center widget inside the allocation
>
> Steffen
>
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