how about emwin WM_PAINT trigger mechanism?

491205517 · Jul 14th 2018, 12:51pm

fresh man alway have much question.

A window has been created.
1. If the text of a text label of the window changed, wether a WM_PAINT message will be sent automatically?
2. the message "WM_POST_PAINT", is "Send to a window after the last WM_PAINT message is sent",
for user's code should be code in WM_POST_PAINT or WM_PRE_PAINT instead of WM_PAINT?

My english is so good.

thanks.

491205517 · Jul 14th 2018, 1:31pm

I set a break point at WM_PAINT, and the point will be broken several times at the first.
After the first period, the point never be broken.

So it means if a window be create, the WM_PAINT will be sent many times during the "create process"?

491205517 · Jul 14th 2018, 1:48pm

case WM_PAINT:
hMem00_Face = GUI_MEMDEV_Create(141, 15, 76, 76);
GUI_MEMDEV_Select(hMem00_Face);
GUI_SetColor(GUI_WHITE);
GUI_SetPenSize(16);
GUI_AA_DrawRoundedRect(149, 23, 209, 83, 30);
GUI_MEMDEV_Select(0);
break;

The hMem00_Face is a global var, I count it will be broken 21 times if I set a break point at the "GUI_MEMDEV_Create" line.
My code is compliled with no Optimzation Level 0.
The code as it, the result is right. But I use the code below, the result is error, acted as no any effect.

case WM_PAINT:
if (WM_HMEM_NULL == hMem00_Face)
{
hMem00_Face = GUI_MEMDEV_Create(141, 15, 76, 76);
}
GUI_MEMDEV_Select(hMem00_Face);
GUI_SetColor(GUI_WHITE);
GUI_SetPenSize(16);
GUI_AA_DrawRoundedRect(149, 23, 209, 83, 30);
GUI_MEMDEV_Select(0);
break;

The hMem00_Face is init as WM_HMEM_NULL.

So if I use the fisrt codes, is there a memory leak happen? And how I delete the memory device?

491205517 · Jul 14th 2018, 8:52pm

sorry, I carefully read the code given by admin schoenen, the memory device creation should be put in WM_CREATE.
thanks.

491205517 · Jul 16th 2018, 11:50am

now I have solve the problem, or I have avoid the problem.

SEGGER - Schoenen · Jul 17th 2018, 9:30am

Hi,

1. If the text of a text label of the window changed, wether a WM_PAINT message will be sent automatically?

Yes, a window will be marked as invalid on creation and receives as many WM_PAINT messages as neccessary to draw the window. A window can receive multiple WM_PAINT messages, due to clipping. The clipping mechanism will leave out areas which don't have to be drawn (like a opaque window on top of the window to be drawn).

Take a look this simple application. Each time the background window gets a WM_PAINT message it uses a different color. It will receive 4 messages, one for each area around the child window.

C Source Code

#include "WM.h"
void _cbBk(WM_MESSAGE * pMsg) {
GUI_COLOR aColor[] = { GUI_BLUE, GUI_GREEN, GUI_RED, GUI_CYAN, GUI_MAGENTA, GUI_YELLOW };
static int Index;
switch (pMsg->MsgId) {
case WM_PAINT:
GUI_SetBkColor(aColor[Index++]);
if (Index == GUI_COUNTOF(aColor)) {
Index = 0;
}
GUI_Clear();
break;
default:
WM_DefaultProc(pMsg);
}
}
void _cbWin(WM_MESSAGE * pMsg) {
switch (pMsg->MsgId) {
case WM_PAINT:
GUI_Clear();
GUI_DispStringAt("Hello world!", 10, 10);
break;
default:
WM_DefaultProc(pMsg);
}
}
void MainTask(void) {
WM_HWIN hWin, hWinBk;
GUI_Init();
hWinBk = WM_CreateWindowAsChild(0, 0, 320, 240, WM_HBKWIN, WM_CF_SHOW, _cbBk, 0);
hWin = WM_CreateWindowAsChild(10, 10, 100, 100, hWinBk, WM_CF_SHOW, _cbWin, 0);
while (1) {
GUI_Delay(100);
}
}

Display All

2. the message "WM_POST_PAINT", is "Send to a window after the last WM_PAINT message is sent",
for user's code should be code in WM_POST_PAINT or WM_PRE_PAINT instead of WM_PAINT?

WM_PAINT is the proper position to place you code if you want to draw something in a window. The pre- and post-messages are seldom used and more for preparing a drawing operation.

Regards,
Sven

491205517 · Jul 21st 2018, 12:35am

thank you.
The problem has been solved.

how about emwin WM_PAINT trigger mechanism?

how about emwin WM_PAINT trigger mechanism?

C Source Code

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