Bug 141140

Summary:

ComplexTextController::offsetForPosition() might erroneously detect a ligature when instead CT simply omitted an invisible glyph

Product:

WebKit

Reporter:

Myles C. Maxfield <mmaxfield>

Component:

Layout and Rendering

Assignee:

Myles C. Maxfield <mmaxfield>

Status:

NEW ---

Severity:

Normal

Priority:

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
Reproduction screenshot	none
Reduction	none

Description Myles C. Maxfield 2015-02-01 11:46:07 PST

Created attachment 245837 [details]
Reproduction screenshot

https://www.opengl.org/wiki/Geometry_Shader
Double click on "triangle_strip" (see screenshot)
Version 8.0.3 (10600.3.18, r179440)
14C109

Comment 1 Myles C. Maxfield 2015-08-27 00:17:16 PDT

Created attachment 260046 [details]
Reduction

Comment 2 Myles C. Maxfield 2015-08-27 00:20:15 PDT

Not due to simple line layout

Comment 3 Myles C. Maxfield 2015-08-27 00:22:14 PDT

For some reason the ZWS is being layed out to be the right half of the "p"

Comment 4 Myles C. Maxfield 2015-08-27 00:44:05 PDT

offsetForPosition() uses the complex text code path. In this code path, when the string ends with a ZWS, CoreText simply doesn't return a glyph for that character.

However, this means that in ComplexTextController::offsetForPosition(), it appears that the last glyph corresponds with two characters (since that ZWS doesn't get its own glyph). This makes us think that we are encountering a ligature, and we put the break between the two code points in the middle of the last glyph.

When you double click, you select the word, without the ZWS. Therefore, the caret gets placed in the middle of the last glyph.