339553 - drawString enhancement for <canvas>

Status: RESOLVED FIXED

(Core :: Graphics: Canvas2D, enhancement)

Description

[Lars Schöning]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.3) Gecko/20060426 Firefox/1.5.0.3
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.3) Gecko/20060426 Firefox/1.5.0.3

As the canvas tag is not a standard anyway may I suggest the addition of a drawString method with parameters for font type, size and string. 

In order to achieve usability canvas really requires an equivalent prototype method, however the established prototype functions take immense amounts of clocktime and significantly (and unnessessarily) slow down the canvas. The current lack of standard in canvas makes it possible to include a drawString method before it is too late, thus adding new possibilities to the object.

Reproducible: Always

Comment 1

[Christian :Biesinger (don't email me, ping me on IRC)]

> As the canvas tag is not a standard anyway

http://whatwg.org/specs/web-apps/current-work/#scs-dynamic

Comment 2

[Anne (:annevk)]

Some ideas have been drafted http://wiki.mozilla.org/Canvas:Text but it would be best if this was discussed at [e-mail] first.

(Note that even if it is a standard it's still possible to extend objects with possibilities following the undrafted rules for extensibility of objects or by proposing additions to such a atandard on the appropriate forums.)

Comment 3

[Lars Schöning]

> > As the canvas tag is not a standard anyway
> 
> http://whatwg.org/specs/web-apps/current-work/#scs-dynamic

It is a working draft.

Comment 4

[Anne (:annevk)]

Right, proposed extensions to such working drafts go to the document author and or the public mailing list attached to it: see comment 2.

Comment 5

[Rob Arnold [:robarnold]]

Attachment: Implements textStyle, drawText, measureText

Comment 6

[Rob Arnold [:robarnold]]

Attachment: Now implements just drawText, measureText, textStyle and one assertion in gfxFont

This patch is dependent on bug 382710

Comment 7

[Rob Arnold [:robarnold]]

Attachment: TextStyle, DrawText, MeasureText, PathText, TextAlongPath

Comment 8

[Rob Arnold [:robarnold]]

Comment on attachment 266941 [details] [diff] [review]
TextStyle, DrawText, MeasureText, PathText, TextAlongPath

Still dependent on aforementioned bug 382710

Comment 9

[Rob Arnold [:robarnold]]

Attachment: Fixes crash when SetTextStyle was not called before the other function calls

Comment 10

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 267311 [details] [diff] [review]
Fixes crash when SetTextStyle was not called before the other function calls

r+ me with name change to moz-prefixed names (mozTextStyle, etc.).  However, please request review from dbaron (or bz?) on the style additions.  Thanks!

Comment 11

[Takeshi Kurosawa :takenspc]

(In reply to comment #10)
> (From update of attachment 267311 [details] [diff] [review])
> r+ me with name change to moz-prefixed names (mozTextStyle, etc.).


According to HTML 5,
> drawing text is not supported in this version of the API
- http://www.whatwg.org/specs/web-apps/current-work/multipage/section-the-canvas.html#the-2d

> Vendors may also define experimental contexts using the syntax vendorname-context, for example, moz-3d. 
- http://www.whatwg.org/specs/web-apps/current-work/multipage/section-the-canvas.html#getcontext


So, we should create another context (e.g. moz-2dtext) as Opera did (opera-2dgame).
http://my.opera.com/WebApplications/blog/show.dml/200788

Comment 12

[Rob Arnold [:robarnold]]

(In reply to comment #11)
> (In reply to comment #10)
> > (From update of attachment 267311 [details] [diff] [review] [details])
> > r+ me with name change to moz-prefixed names (mozTextStyle, etc.).
> 
> 
> According to HTML 5, drawing text is not supported in this version of the API

Which is why we are going to prefix our extension with moz so that when such an api is standardized, this implementation will not conflict.

> Vendors may also define experimental contexts using the syntax vendorname-context, for example, moz-3d. 
> -
> http://www.whatwg.org/specs/web-apps/current-work/multipage/section-the-canvas.html#getcontext

I interpret this as stating that it is not required to define another context. Also note that the same document states:
> UA must return a reference to an object implementing CanvasRenderingContext2D

The object we return does implement this interface.

> So, we should create another context (e.g. moz-2dtext) as Opera did
> (opera-2dgame).
> http://my.opera.com/WebApplications/blog/show.dml/200788

Perhaps, but given that we are prefixing our extension functions to avoid future naming collisions (unlike Opera), there is not as much of a reason to do this.

Comment 13

[Rob Arnold [:robarnold]]

Attachment: Method/Attribute renaming and fixed a bug when the canvas was not attached to the dom

Comment 14

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 269917 [details] [diff] [review]
Method/Attribute renaming and fixed a bug when the canvas was not attached to the dom

Looks good

Comment 15

[Rob Arnold [:robarnold]]

Attachment: Fixed builds errors on trunk

gfxGlobalTextRunCache disappeared between when I posted and vlad review. New version uses gfxTextRunCache::AutoTextRun.

Comment 16

[Rob Arnold [:robarnold]]

Attachment: Text path demo

Comment 17

[Rob Arnold [:robarnold]]

Attachment: Second path demo

Comment 18

[Rob Arnold [:robarnold]]

Attachment: Animated text demo

Comment 19

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Thanks.. this is still on my list to check in, my tree's just been full of new cairo, but I should have that wrapped up soon.  I'll get this in tonight or tomorrow.

Comment 20

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Checking in content/canvas/src/nsCanvasRenderingContext2D.cpp;
/cvsroot/mozilla/content/canvas/src/nsCanvasRenderingContext2D.cpp,v  <--  nsCanvasRenderingContext2D.cpp
new revision: 1.90; previous revision: 1.89
done
Checking in layout/style/nsStyleSet.cpp;
/cvsroot/mozilla/layout/style/nsStyleSet.cpp,v  <--  nsStyleSet.cpp
new revision: 3.185; previous revision: 3.184
done
Checking in layout/style/nsStyleSet.h;
/cvsroot/mozilla/layout/style/nsStyleSet.h,v  <--  nsStyleSet.h
new revision: 3.23; previous revision: 3.22
done
Checking in gfx/thebes/src/gfxFont.cpp;
/cvsroot/mozilla/gfx/thebes/src/gfxFont.cpp,v  <--  gfxFont.cpp
new revision: 1.58; previous revision: 1.57
done
Checking in dom/public/idl/canvas/nsIDOMCanvasRenderingContext2D.idl;
/cvsroot/mozilla/dom/public/idl/canvas/nsIDOMCanvasRenderingContext2D.idl,v  <--  nsIDOMCanvasRenderingContext2D.idl
new revision: 1.6; previous revision: 1.5
done

Comment 21

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 273496 [details] [diff] [review]
Fixed builds errors on trunk

(was already reviewed and checked in)

Comment 22

[Rob Arnold [:robarnold]]

Attachment: This fixes an issue in Windows optimized builds with some uninitialized data

Comment 23

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Comment on attachment 275020 [details] [diff] [review]
This fixes an issue in Windows optimized builds with some uninitialized data

r+a=me, checked in, thanks!

Comment 24

[Nickolay_Ponomarev]

http://developer.mozilla.org/en/docs/Canvas:Text has some docs (thanks Rob!), but it could use more detail (i.e. formal API documentation), so keeping on the dev-doc-needed radar.

Comment 25

[Eric Shepherd [:sheppy]]

The docs have been overhauled substantially.  Basically the same content, just rearranged to match other reference documents more closely.

http://developer.mozilla.org/en/docs/Drawing_text_using_a_canvas