Custom drawing in Gtk3 with Cairo is explained in https://developer.gnome.org/gtk3/stable/ch01s05.html
Here draw_brush in the handler for motion-notify-event draws small rectangles as the mouse is dragged. In the original code there is no other drawing. Suppose I draw a filled blue rectangle in draw_cb by adding the following code:
cairo_set_source_rgb(cr,0.1,0.1,0.8);
cairo_rectangle(cr,80,80,50,50);
cairo_fill(cr);
and similarly another filled red rectangle in clear_surface which is called from configure_event_cb, I get a strange behavior where the blue rectangle is not over-written by draw-brush, but the red rectangle gets over-written, as seen in the picture below:
Can anyone explain this behavior so that I can correctly make custom drawings in the application I am developing.
So, in clear_surface / configure_event_cb, you draw to surface, which is also the surface where the brush draws to. Since the brush is drawn later, it ends up ontop of the red rectangle that you draw here.
In draw_cb, this temporary surface that is used for the drawing is copied to the screen. If you draw a blue rectangle afterwards to the screen, this blue rectangle ends up ontop of what you drew before.
So basically: The reason is the two different targets for drawing that are used here. One is the "actual stuff" on screen, which can disappear at any time. The other is an internal surface created in configure_event_cb that does not go away unexpectedly.
Related
I need to draw a border or rectangle like a bill payment on shop.
For make it's as real, I need to draw a shredding effect with the bottom is a saw-tooth line instead of a normal border.
Would you please to give me some advises?
Forget borders. Terminate the bottom side of the white area as a normal rectangle, but stack immediately at bottom an image (e.g. PNG) with the perforation strip.
That's the easiest way, unless you need something that adapts to the rectangle's width.
I'm having a problem that's driving me crazy for a couple hours...
Situation:
I am drawing a shape - ellipse,
then im creating a new brush - from an image,
I apply the brush to my shape,
and then I rotate the shape..
The problem is: Everthying is displaying correctly - but...
As soon as I drag the shape to the edge of the window - thats where the formular ends,
it's starting to cut of some parts of the shape.
It's simply not drawing the part that should be not visible, because overflowing the form.
But in my case, I've rotated the shape, so it's cutting the wrong part of it.
This is what it look's like. Is there a way to kinda "reset" the cliping.. Or another solution...
Solved It.
Set the parent element's width and height larger then the window is (its was HorizontalAlignment.Stretch) before.
Now you'll never reach the cliping edge of the parent
I'm building a form with two layers of controls. The bottom layer is a set of Panels with defined properties, one of which is a color different from the form background. The top layer is a set of picture boxes I'm using to display a circle. I've set the PictureBox Background to Color.Transparent, and I've offset it from the underlying Panel by one pixel to get the form to draw the underlying Panel. However, the area around the circle in the PictureBox is displaying the Form Background color, not the panel color. I don't want to draw the circle in the Panel, because I want the circles to move between Panels, and actually look like just a circle that's floating across the form independent of the Panel board underneath. Think of the effect as moving a piece on a board game (you see the peg move across the board, possibly on a diagonal not following the normal game path, then stop in a place on the game).
How can I get the PictureBox to have the underlying Form and panels show through, not just the form background color? I'm using C# Visual Studio 2010, and I'm not a terribly experienced programmer, so a code example would be helpful. An image of the form is at:
http://www.imageurlhost.com/images/salgmpcxvcz830c3flt.jpg
Found a way around the problem. I got rid of the Panels for the spaces in the game, and instead drew them as rectangles on the form's background image.
http://www.youtube.com/watch?v=gZNdfVwkttM - you can see all of the problem described on this video if you can't see pictures.
All of walls in all images below have a semitransparent PNG texture. Each square wall, floor and ceiling tile is a separate GeometryModel3D (I know that is no good for performance but...). The floor and the ceiling of the central cube have no any geometry and textures - so they have a color the same as Window.Background (black). But the effect considered appears in any way of transparency obtaining: texture for ImageBrush with transparency, Material.Color (for example DiffuseMAterial.Color) where Color has alpha channel, ImageBrush as material where ImageBrush has Opacity - all the way I have the same problem.
All of walls consists of two triangles. Where are no explicit normals , because I define triangle indices so normals culculated automatically by WPF.
http://imagepost.ru/images/i/ma/image00001.png
It also haven't any back material or extra triangles from the back side.
As you can see there is no problem if you look only from +Z to -Z (standing on the blue square and looking to the red square - that is the second picture).
But if you look backward (from red to blue - the first picture) there is no transparency!
Well, I desided to look from the yellow square (third picture).
And then I walked nearer - you can see what was happening (pictures from 4 to 6).
There are no geometry construction error or texture mapping error or lighting error! It is some kind of clipping, I guessed! In addition there are some interested pictures 7 and 8 to prove my guess.
The last picture shows the white background of the window that hosted Viewport3D (previous was black), and my guess about clipping confirmed - WPF just not painted this part of the scene and we can see the window background!
BUT! If this happens from various looks, why the look from +Z to -Z (second picture) seems well?!
You need to sort the triangles based on their distances from the viewpoint. Only then, wpf will be able to blend the transparent textures.
DirectX is able to blend triangles on top of each other but only when drawing them back to front
http://www.ericsink.com/wpf3d/2_Transparency.html
I'm trying to modify the default graph viewer of the Graph# library because its user interface is awful (just try dragging a node outside of the boundaries, you'll see!)
The basic setup is this: there is a GraphCanvas control (inherited from Panel) which has children of Vertex and Edge control types. What I want to achieve is:
GraphCanvas has scroll bars if the contents do not fit in the screen;
GraphCanvas can also be scrolled by "dragging" it (just click on an empty space and drag);
GraphCanvas can be zoomed in and out (via CTRL+mouse wheel);
Vertices can be dragged around. If a vertex is dragged outside the current boundaries of GraphCanvas, the boundaries are increased. The scroll bars should reflect this, however the current viewport should not scroll away while the vertex is being dragged . The same goes if dragging a vertex reduces the boundaries of GraphCanvas - it should stay the same size until the drag operation is finished and resize only then. Automatically scrolling the viewport during a drag operation is awfully confusing and easily introduces dragging errors. See the original implementation if you want to know what I mean.
Although I've got a fair bit of experience with .NET, I'm still a complete beginner in WPF. My current attempt is (in the measure/arrange layout phase) to give each vertext the XY coordinate it desires (even if negative) and implement zooming/scrolling by handling mouse events on the GraphCanvas and modifying the RenderTransform property. Dragging just changes the XY coordinates on the specific vertex (probably triggering the re-layout of the whole thing which would be nice to avoid too). Scrollbars are implemented by placing the GraphCanvas inside a ScrollViewer and implementing IScrollInfo on the GraphCanvas.
Unfortunately there seems to be a problem: I can get mouse events on the GraphCanvas itself only if it has a background at the point. That would be OK, I want a white background anyway, but in the negative coordinates of the GraphCanvas it does not draw the background - and thus does not respond to mouse events.
I'm also wondering if I'm doing the Right Thing by allowing all my child controls (vertices and edges) to go into negative coordinates. How would you implement this?
Added: To clarify about the background problem check out the following screenshot:
(source: valts.21.lv)
What you see here is a simple Windows Forms form with a WPF Host control on it. That has a ScrollViewer in it, and the ScrollViewer has the GraphCanvas in it. The GraphCanvas contains 4 vertices and 6 edges.
The GraphCanvas is stretched to fill the ScrollViewer. But since some of the vertices are at negative coordinates, it has a RenderTransform applied which simply shifts everything to the right (TranslateTransform). It also has a white background brush.
Note the gray area on the left. That's still a part of the GraphCanvas, but the background brush somehow doesn't exted there. Also, if I left-click there with my mouse (not on a node, but on the gray area), I do NOT get an event. If I left-click on the white area, I get all events just fine.
Call CaptureMouse on canvas.mouseDown and ReleaseMouseCapture on mouse up. Also, if you set your canvas background to transparent it will still be hit testable
You can attach a 'Draggable' behavior to each element.