I have a tablet with a stylus, in normal operation it's easy to draw and figure out where the stylus is since hardware feeds the correct coordinates. Then i rotate the monitor 90 º via ChangeDisplaySettingsEx API, in this situation i have to apply a translation (2nd monitor) + rotation which i'd like to avoid. Then i read about this style DS_ABSALIGN in MSDN:
Indicates that the coordinates of the dialog box are screen
coordinates. If this style is not specified, the coordinates are
client coordinates.
I'd like to draw to a DC in screen coordinates which is what i'm being feeded, not client coordinates, but defining that style doesn't make any difference.
//unaffected by the style
DrawIcon(hDevCtx, m_Point.x, m_Point.y, LoadCursor(NULL, IDC_ARROW));
Is it there any way to draw an icon in screen coordinates?
edit: finally i had no choice but to do the calculations for every turn so i close the question
The coordinates you pass to DrawIcon() depend on the kind of DC you have. For example let's say you used GetDC() to get the DC. If you pass it a window handle, the coordinates you pass to DrawIcon() will be relative to the client area of that window. If you pass 0 to GetDC() the coordinates will be relative to desktop screen. If you want to draw on desktop screen then use GetDC(0) or a better method if there is one. If you just want to convert screen coordinates to client coordinates or vice versa use ScreenToClient() or ClientToScreen()
Related
My project combines a projection screen with a head tracking device, where the screen should act as a window through which I could see my virtual "world". Basically, this.
Initially, I thought this would be easy: Map the camera position to the head tracking, have it point towards my window in the virtual world, adjust camera parameters to fit its frustum to the window, and voilà!
Except it doesn't work because I'm viewing the window (both real and virtual) at an angle, so the regular perspective camera doesn't do the trick: If I understand correctly, that camera 'input' is always rectangular, but I need to 'fit' it in a trapezoïd instead.
I think I should be able to achieve that by making my own projection matrix, but I'm a bit lost on how to do that: I have played a bit with basic matrix transforms (translate, scale, rotate), but I have zero experience with more complex stuff (ie perspective).
My best guess for now is trying to deduce the projection matrix from known transformed points (the corners of my window => the corners of the screen) but I feel like it's going to be quite expensive to do that each frame, and that doesn't account for the perspective inside the "window".
thanks for any help!
Is it possible to move the background image in app inventor?
I'm trying to use the call canvas background pixel color block to get the color of different parts of the background. If I can't move the background image, can I use math blocks to change the x and y parts of the call canvas background pixel color block to a variable?
Important Note
I am referring to the image sprite, under the drawings and animations tab.
An image will have coordinates once you put it inside of a canvas. In order to move it, create 2 sliders with 2 balls and 2 narrow canvases that are (seemingly) equal to the ball's diameter. (Place underneath the image, make sure the image isn't too big)
Go into blocks and place the "when dragged" command, and hook up the change in the ball's x/y to the change of the images x/y. (Assuming you know how to make the ball move while you drag it, also very simplistic). This will make the image's movement equal to the ball's movement (1:1 ratio) Depending on how much you want the image to move, your'e going to have to implement a ratio.
When you drag the ball(s), the image should move with it.
Is there a way (API) of getting the size (vertical and horizontal) in pixels of the resize corners?
I am referring to the area at each of the corners of a window where you can resize the window in both directions (Left-to-Right and Top-to-Bottom) at the same time using your mouse. You will know you are there with your mouse cursor when you hover over the corners of the window and the mouse cursor is a Diagonal Resizing cursor.
Thank you
Edit:
An example: Hover your mouse over the right edge of a sizable window. Start in the middle (vertically) of the window and move the mouse up along the edge until the horizontal sizing cursor changes to a diagonal sizing cursor. How do I determine by asking the OS how far that position when the cursor changes, is from the top of the window.
I would suggest to use the size of the scrollbars. Call GetSystemMetrics with SM_CYHSCROLL and SM_CXVSCROLL. May be also SM_CYSIZEFRAME and SM_CXSIZEFRAME sizes can be combined.
But I think a better value is to use the height of the status bar. However even Microsoft Windows seems to use some fixed value as can seen on the screenshot.
Comparing the results of GetClientRect and GetWindowRect will tell you how wide the non-client (border) area is along each edge of the window.
If you're concerned that it might not all be active for sizing (true especially along the top), or you want to distinguish the diagonal sizing areas from edge sizing areas, you can take the coordinates discovered in step 1 and pass them to SendMessage(WM_NCHITTEST) See its documentation for the various return codes. There's no problem sending this message repeatedly -- it's designed to be called for each mouse move event and therefore is very fast.
Aero glass causes alot of people problems trying to draw on it. Anything with an alpha value of 255 seems to be treated as transparent with DWM using an additive blur to draw it. I want a part of client area to use Aero glass with the rest of it treated as opaque, so I don't have to deal with the headache of common controls not rendering properly.
MSDN lists a function DwmEnableBlurBehindWindow which lets you mark part of the client area as blurred by DWM. It takes a DWM_BLURBEHIND pointer which which has an HRGN handle to the region of the window. When I use this function, the entire window becomes transparent with an additive blend, but only the region of the window I passed to DwmEnableBlurBehindWindow gets blurred. Is there a way I can keep the rest of the window from becoming transparent?
What I have looks a bit like:
blur.dwFlags = DWM_BB_ENABLE | DWM_BB_BLURREGION;
blur.hRgnBlur = CreateRectRgn(0, 0, 90, 90);
blur.fEnable = true;
DwmEnableBlurBehindWindow(hwnd, &blur);
RECT rect;
GetClientArea(&rect);
FillRect(hdc, &rect, CreateSolidBrush(0));
From the MSDN Library article:
The alpha values in the window are honored and the rendering atop the blur will use these alpha values. It is the applications responsiblity for ensuring that the alpha values of all pixels in the window are correct. Some GDI operations do not perserve alpha values so care must be taken when presenting child windows as the alpha values they contribute are unpredicitable.
Make that most GDI operations, like FillRect(). The brush you created is drawn with 24-bit colors, the alpha will be 0. Which makes the window transparent. You'll need to switch to, say, GDI+. Text is particularly troublesome. As well as legacy Windows controls, like EDIT and LISTBOX which draw with GDI.
I'm using GDI+ in my application, and I need to use a rotated LinearGradientBrush to paint several rects in the exact same way. However, although I'm calling the same code to fill each rect, the results aren't what I expect. Here's the code to create the gradient fill, where rcDraw is the rect containing the area to paint for each rect. These coordinates are in the parent window's coordinates, so they are not identical for the 2 rects.
g_hbrLinear = new LinearGradientBrush( Rect( 0, rcDraw.top, 0, rcDraw.bottom - rcDraw.top ),
clrStart, clrEnd, (REAL) 80, FALSE );
What I see on screen looks like this (http://www.nnanime.com/bugs/LinGradBrush-rotate10.png). You can see that it's as if the fill from the first rect continues into the second one. What I really want is to have the 2 rects look identical. I think I can do that if I paint each rect separately using its own client coordinates, but for the purposes of my app, I need to use the parent window's coordinates.
I guess what I'm asking is, how does GDI+ calculate the "origin" of a fill? Is it always based on 0,0 in the coordinate system you use? Is there a way to shift it? I tried TranslateTransform, but it doesn't seem to shift the fill in a way that I find predictable or understandable.
The rect passed to the linear gradient brush determines the where the left and right colors will sit, and the gradient will be painted within this rectangle.
So, I think you need to create a brush for each rectangle you are painting, where the rectangle you are painting is also passed to the constructor for the linear gradient brush.
My experience with the "transform" of linear gradient brushes matches yours; I haven't been able to understand what it's supposed to do.
You can think of a brush in GDI+ as a function mapping world co-ordinates to a color. What the brush looks like at a given point does not change based on the shape being filled.
It does change with the transform of the Graphics object you're drawing on. So, if you don't want to change the brush, you could temporarily change the transform of the Graphics object so that the rectangle you're drawing has a specific, known size and position in world coordinates. The BeginContainer and EndContainer methods should make this easy.
(There is also the RenderingOrigin property but it only affects hatch brushes, which oddly are unaffected by world transforms.)