Solved

Drawing to the screen

Posted on 2000-03-17
7
251 Views
Last Modified: 2010-04-02

I am in a dialog box.  the m_Picture is a Picture control (static).

CDC *testdc;
testdc = m_Picture.GetWindowDC();
testdc->SetMapMode(MM_HIENGLISH);
CPen pen5;
pen5.CreatePen(PS_SOLID, 1, RGB(255,0,0));
testdc->SelectObject(&pen5);
testdc->Rectangle(0,0,500,500);
CPen pen6;
pen6.CreatePen(PS_SOLID, 1, RGB(255,0,0));
testdc->SelectObject(&pen6);
CRect rec;
m_Picture.GetClientRect(&rec);
testdc->DPtoLP(&rec);  
//tried w/ & w/out
testdc->MoveTo(rec.top, rec.left);
testdc->LineTo(rec.bottom, rec.right);

Nothing comes out.  Am I doing something wrong.
0
Comment
Question by:jaiken
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
7 Comments
 
LVL 22

Expert Comment

by:nietod
ID: 2628828
The problem is the mapping mode.  In MM_HIENGLISH mode the Y value increases in the upward direction.  Bot the origin will be the upper-left corner of the window so the window lies in the negative Y portion of the XY plane.  But you are specifying coordinates that are positive Y, i.e. above the window.
0
 

Author Comment

by:jaiken
ID: 2629221
I did change the MoveTo and LineTo (because I had the x/y backwards) but looking at rec upon return from GetClientRect and DPtoLP the y.bottom is a negative value.  I get (0,0) and (2056, -2555).  NOTE:  I also got rid of the drawing of the rectangle to be more simple.


CDC *testdc;
testdc = m_Picture.GetWindowDC();
testdc->SetMapMode(MM_HIENGLISH);
CPen pen6;
pen6.CreatePen(PS_SOLID, 1, RGB(255,0,0));
testdc->SelectObject(&pen6);
CRect rec;
m_Picture.GetClientRect(&rec);
testdc->DPtoLP(&rec);
testdc->MoveTo(rec.left, rec.top);
testdc->LineTo(rec.right, rec.bottom);
 
0
 
LVL 22

Expert Comment

by:nietod
ID: 2629279
Why do you use GetWindowDc() instead of GetDC?

Is the window open and visible?
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Accepted Solution

by:
fmharr earned 15 total points
ID: 2629570
Get rid of the GetWindowDC and use:

testdc = m_Picture.GetDC();

get rid of the SetMapMode

get rid of the DPtoLP

all the rest is fine... the default system is 0,0 == top/left and +,+ values going down and right.

with the above changes you should have a line from the top-left to the bottom-right in red!

also, you need to put the code in the OnDraw() function or some button function and not in the InitDialog() event!  You also need to save/restore the DC so you wont have resource leeks!

0
 
LVL 22

Expert Comment

by:nietod
ID: 2629620
I already pointed out that he should PROBABLY be using GetDC().  I don't think there is any evidence that the code is in InitDialog().
0
 
LVL 22

Expert Comment

by:nietod
ID: 2629874
What was the problem?
0
 

Author Comment

by:jaiken
ID: 2635735
I didn't have the code in the right place (OnDraw) function.
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In days of old, returning something by value from a function in C++ was necessarily avoided because it would, invariably, involve one or even two copies of the object being created and potentially costly calls to a copy-constructor and destructor. A…
What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

623 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question