[Laszlo-dev] anybody recall why we changed how LzTextSprite.getTextWidth works from 4.2 ?

[P T Withington]

Before I did this, I would _really_ want to understand why it was changed.  It seems this was the end result of a _lot_ of discussion related to:

http://jira.openlaszlo.org/jira/browse/LPP-6580

You, Max, and André all had input on this.

getTextWidth is a Kernel API, which is used by the LFC.  So, it needs to have a contract that is the _same_ for all platforms.

I changed this and left a note as to why:

/**
 * Calculates the current width of the text held by the text field.
 *
 * @devnote NOTE: [2009-03-01 ptw] this is _not_ the clip textWidth, which
 * "when autoSize is true is always 4 pixels less than _width" (which
 * is why we have to add 4 pixels for emulate_flash_font_metrics
 * in the DHTML version of this method, and why Henry used to add
 * PAD_TEXTWIDTH to the textWidth!)
 *
 * @devnote NOTE: [2009-03-28 ptw] But if the text is empty, we return
 * 0.  <sigh />
 */

The way I read that, when we split the LFC to have platform kernels we screwed up the abstraction and left part of the platform-specific stuff (this 4px offset from the Flash API) in the general part of the kernel.  This change fixes that, so that _all_ the kernels are measuring the same thing.

You clearly cannot just change the Flash kernel, because then it would be skewed from the other kernels.

On 2010-04-01, at 14:08, Henry Minsky wrote:

> We used to measure text width in LzTextSprite by looking at the Flash
> 'TextField.textWidth' property (and adding
> 4 pixels of padding because it clipped otherwise).
> 
> At some point that method was changed to look at the TextField._width
> instead, which gives different values (slightly larger ones).
> 
> Anyone remember what the thinking there was? I'm inclined to revert that, so
> that we're compatible with the
> 4.2 text width in swf8.
> 
> 
> 
> r13517  by ptw has the last assignment according to svn blame
> 
> " Fixed getTextWidth, getTextHeight, getTextfieldHeight,
>    to obey kernel API contract."
> 
> 
> 
> -- 
> Henry Minsky
> Software Architect
> hminsky at laszlosystems.com