Grid dots do not recognize alpha

[Kelvin Song]

When you turn on the "Show dots instead of lines" option in the grid settings, the major and minor colors are all set to full opacity. This can get really distracting when working with pictures with a lot of color contrast. I get that with lows alphas the dots seem to disappear but you can still get the opaque dots by cranking up the alpha to 255.

Attached a patch that fixes the problem

[su_v (suv-lp)]

With current stable 0.48.5 and trunk r13520 on OS X 10.7.5, the dots drawn at major grid lines intersections do respect the alpha value of the grid line color, only the smaller ones drawn at minor grid intersections don't.

[Kelvin Song (kelvinsong)]

I am sorry but this is simply not true. None of the dots respect alpha, only the periphery of the major grid dots changes with the alpha (see attached screenshot). The core of the major grid dots still ignores alpha. Also I don't see why this fix should be rejected just because the bug "only affects the minor dots"...

[Kelvin Song (kelvinsong)]

also I see that this bug has been assigned to me what does that mean? Sorry I'm pretty new to launchpad...

[su_v (suv-lp)]

Who said a single word about rejecting your patch?

[su_v (suv-lp)]

Reverting assignment, too.

[su_v (suv-lp)]

Apparently I checked the current state not carefully enough, sorry about.

[Kelvin Song (kelvinsong)]

sorry you just tagged the bug as "wishlist" so I figured you were giving a reason to close

[jazzynico (jazzynico)]

The dotted grid were added revision 2915 (http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/2915) with the current color values (alpha not used).

@Johan, do you remember why that choice was made?

[Johan Engelen (johanengelen)]

I don't remember why I did that. I think it was to have nice behavior when toggling between grid lines and dots. If you enable alpha, switching from lines to dots makes the dots very hard to see if one does not crank up the alpha. So easy toggling is no longer possible. I don't know how common that use case is.

[Formerly Kevin Yin, now disabled (kyin)]

Sliding the alpha up and down reveals that each grid dot in fact consists of two elements: a point and a cross. The cross respects alpha but the point does not.

[Formerly Kevin Yin, now disabled (kyin)]

Some idle speculation: the difference in alpha treatment might be a trick to allow the user to choose either crosses or points. If so, there are several ways to go about changing the behavior.

[Tavmjong Bah (tavmjong-free)]

If the alpha is set for dots as it is set for lines, the dots become barely visible. To maintain a similar visual impact the alpha for dots needs to be increased, but as pointed out here, setting it to its maximal value can be too much.

I've patched the code to increase the alpha when using dots by a factor of four (of course, clamped by full opacity). This seems to give a similar visual impact but still allows a user to lower the alpha if needed.

The alpha treatment for dot/cross was/is simply to emphasize the major grid points.

[su_v (suv-lp)]

Fix committed in rev 14114:
http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/14114