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IDProjectCategoryView StatusLast Update
0009018ScribusShape Drawingpublic2010-04-15 22:38
Reporterpspencer Assigned Tojghali  
PrioritynormalSeverityminorReproducibilityalways
Status closedResolutionduplicate 
PlatformlinuxOSFedoraOS Version10
Product Version1.3.6 
Summary0009018: Constraining Angle while Drawing Lines is Inaccurate in Certain Circumstances
DescriptionWhen you attempt to draw a straight horizontal line by clicking on the line-drawing tool and drawing a line with the control key held down, it is not always quite horizontal. The shorter the line, the worse the deviation, sometimes several degrees from zero.

This only happens for certain settings of display resolution (e.g. 100 dpi) and is likely related to problems with how scribus maps document coordinates to window pixels.
Steps To ReproduceIn Preferences, set Display Resolution to 100 dpi.

Create a new document. Set document units to inches.

For simplicity, set 0in scratch space above document (though problem occurs with nonzero scratch space too) so the top of the document ought to exactly coincide with the top of the canvas, which in turn ought to exactly coincide with the top viewing area of the window.

Zoom document at 100% and ensure it is scrolled all the way to the top.

Click on line drawing tool. Move the mouse to try to select the point at (1in, 1in) -- note that you can't; as you move the mouse down pixel by pixel, you will see coordinates of 0.9892in, 0.9992in, 1.0092in.

Click when the y-coordinate shows as 0.9992in. Hold the control key down and
drag mouse to the right about 0.5 inch.

You will see the constrained angle shows at well over 2 degrees (and drops closer to zero the longer you make the line), and the resulting line should you release the mouse there is definitely not horizontal.

This is on Linux, in case this is an operating-specific problem.

If I repeat the above procedure with display dpi set to 72dpi in preferences, I get no problem. I also see that I am able to exactly get 1inch as the y-coordinate of the first point on the line; the coordinates I see as I move the mouse down prior to clicking on the first line point are 0.9722, 0.9861, 1.0000, 1.0139 which is exactly what I expect, moving in increments of 1/72 of an inch (= approx 0.0139 inches) with 1 inch exactly lining up with a pixel.

Evidently, when dpi=100, the top pixel in the window is not properly lined up with the top edge of the document, but the constraint code assumes it is.
TagsNo tags attached.
Patch

Relationships

duplicate of 0008960 closedjghali Initial drawing of a line with CTRL doesn't produce the correct angles 

Activities

jghali

2010-04-15 22:38

administrator   ~0023705

This issue has already been fixed in 1.3.7svn as 0008960

Issue History

Date Modified Username Field Change
2010-04-14 18:33 pspencer New Issue
2010-04-15 22:38 jghali Note Added: 0023705
2010-04-15 22:38 jghali Relationship added duplicate of 0008960
2010-04-15 22:38 jghali Status new => resolved
2010-04-15 22:38 jghali Resolution open => duplicate
2010-04-15 22:38 jghali Assigned To => jghali
2010-04-15 22:38 jghali Status resolved => closed