Re: [fltk.general] Strange artefacts visible on controls - Forums

On Wed, 6 Jul 2022 at 11:54, Jck_01 wrote:
Hello,
I create the application with the FLTK library. Almost everything works as it should, except one important thing, and I couldn't find the right solution so far. Random artifacts appear in the window. They also appear randomly - sometimes everything is displayed correctly, but sometimes there are strange lines, some parts of the controls are not refreshed etc. I tried to use Fl::check() but it didn't help in every case. Please see the included examples (a strange black line over the window, a strange blue line over the button, and a broken frame around the button). How can I avoid these problems?

We'd probably have to see some code to tell, but to me it looks like you are drawing outside the valid context.

Hmm; Is this on Windows?

Yes, this is on Windows 10.

The order and setting of the "pens" in Windows is a bit sensitive, so you need to ensure you do that in the correct order too. I think that is discussed in the docs, FWIW.
Maybe you can post a small, compile-able example that shows what you are doing that gets this effect?

I will show only most important parts of the code since it involves many classes and is quite complicated.

First I create the dialog window as the new class where inside I define the pointer to the Fl_window.
using WindowPtr = std::unique_ptr<Fl_Window>;

WindowPtr windowPtr;

Then, in the class I create the controls, for example:
windowPtr = std::make_unique<Fl_Window>(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);

connectToServerButton = std::make_unique<Fl_Button>(20, 268, 200, 30, nullptr);
connectToServerButton->copy_label(gui.getTranslation().Translate(u8"Connect to server").c_str());
connectToServerButton->callback(connectToServerCallback, this);

windowPtr->end();

Then, in the connectToServerCallback() callback I do following (netMessages is a multiline edit control):

netMessages->value(u8"");
addMessage(gui.getTranslation().Translate(u8"Connecting to server..."));
Fl::check();
int ret = gui.getNet().getClient().start(); // starting the network client
if (ret != Network::NET_OK) // error
{
}
else // client connected to server
{
addMessage(gui.getTranslation().Translate(u8"Connected!").c_str());
connectToServerButton->deactivate();
}

When I click the connectToServerButton, I sometime receive the artifacts on the whole dialog or on button.