[GUACAMOLE-282] Common surface transfer functions incorrect with respect to alpha channel

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.9.12-incubating
• Fix Version/s: 0.9.13-incubating
• Component/s: guacamole-server
• Assignee: Mike Jumper
• Reporter: Mike Jumper
• Created: 24/Apr/17 18:56
• Updated: 07/Jun/17 15:36
• Resolved: 27/Apr/17 03:52

Description

The common surface implementation used within guacamole-server is incorrect with respect to binary transfer functions as of GUACAMOLE-188, which added support for the alpha channel to the common surface.

Prior to GUACAMOLE-188, the common surface supported only the red, green, and blue channels, thus simple binary operations correctly mirrored those of the JavaScript Guacamole client.

After GUACAMOLE-188, the contents of a surface might have alpha channel values, which are not supposed to be taken into account for all transfer functions. The JavaScript client actually only pays attention to the alpha channel for the following transfer functions:

• GUAC_TRANSFER_BINARY_SRC (alpha channel becomes a copy of source)
• GUAC_TRANSFER_BINARY_NSRC (alpha channel becomes a copy of source and is NOT INVERTED)

In all other cases, the alpha channel of the destination is preserved.

The common surface must be modified to duplicate this behavior.

Issue Links

• is duplicated by: GUACAMOLE-318 RDP to fullclient or terminal server has issue with using putty
• is duplicated by: GUACAMOLE-319 RDP to fullclient or terminal server has issue using Lotus Notes
• relates to: GUACAMOLE-188 Support alpha transparency in guac_common_surface