Such gap can be caused by either texture filtering or by using a sprite that has dimensions that are not dividable by 2.
The fix for the former is to add a border to your sprite by editing the sprite (click the Edit button). After giving it a border you can also use Advanced sprite drawing option and turning off everything except center.
I tried this but it's the same.I set all my texture type "GUI" and filter Mode Point and the grid sprite is 40*40 .
I suspect if it due to the atlas.If I use UITexture , they are fine, but if I use UISprite and get texture from the atlas , the problem happened.
Here is my test scene . You can see the gap problem inthe gridPanel and other two problems in fontPanel.
No visible gaps on my end, but my console log is full of errors because you put UISprites and UITextures on the same object.
Make sure your game window's dimensions are dividable by two. Generally when you use Maximize on Play, they often aren't. Although if you forced it to 1024x768 they should be.
In any case, if you want to eliminate such issues when zooming in / out (non-pixel perfect sprites), then you should give your sprite a border by editing the sprite within the atlas and clicking the "Add a Clamped Border" button. Just keep in mind that this adds +2 to your sprite's dimensions, so your 40x40 sprites will now be 42x42. You should then use Advanced type rather than Simple (chosen on UISprite), with left, right, top and bottom set to Invisible.
No, I use Windows. What dimensions do you see in the "Stats" window?