Accessing IDWriteTextFormat instead of creaing new (FW1FontWrapper line spacing) - c++

Question

I'm using FW1FontWrapper library to wrap the font using in my DirectX 11 C++ application.
I want to change the line spacing (distance between two lines of text) in the text rendered with FW1FontWrapper.
I know that in DirectX I can use to it IDWriteTextFormat::SetLineSpacing(DWRITE_LINE_SPACING_METHOD_UNIFORM, 30.0f, 20.0f).
Unfortunatelly, I don't know how to access the right IDWriteTextFormat structure.
I have tried to:
HRESULT hResult = FW1CreateFactory(FW1_VERSION, &FW1Factory);
hResult = FW1Factory->CreateFontWrapper(device, L"Arial", &fontWrapper);
//my attemp - first get the IDWriteFactory
IDWriteFactory *pDWriteFactory;
hResult = fontWrapper->GetDWriteFactory(&pDWriteFactory);
//and now the IDWriteTextFormat
IDWriteTextFormat *pTextFormat;
hResult = pDWriteFactory->CreateTextFormat(L"Arial", NULL,
DWRITE_FONT_WEIGHT_NORMAL, DWRITE_FONT_STYLE_NORMAL,
DWRITE_FONT_STRETCH_NORMAL, 10.0f, L"", &pTextFormat);
pTextFormat->SetLineSpacing(DWRITE_LINE_SPACING_METHOD_UNIFORM, 100.f, 20.0f);
I guess it doesn't work, because that way I create and modify the new IDWriteTextFormat, not the one that will have affect on the rendering by:
fontWrapper->DrawString(
context,
s2ws(content).c_str(),// String
fontSize,// Font size
startTextPosition.getX(),// X position
startTextPosition.getY(),// Y position
color,// Text color, 0xAaBbGgRr
FW1_RESTORESTATE// Flags (for example FW1_RESTORESTATE to keep
//context states unchanged)
);
So, how access the right IDWriteTextFormat (the one that when I will modify, will have impact on the rendering; not the new one)?
As far as I know FW1FontWrapper has no own method to set line spacing.

Answer 1

Looking at the source code of the FW1FontWrapper module, you can see that DrawString internally uses a default IDWriteTextFormat that you can't access.
The solution is to use DrawTextLayout instead of DrawString.
To do this (using your variable names), first create the factory and IFW1FontWrapper as in your existing code:
HRESULT hResult = FW1CreateFactory(FW1_VERSION, &FW1Factory);
hResult = FW1Factory->CreateFontWrapper(device, L"Arial", &fontWrapper);
Then get the DWrite factory and create the IDWriteTextFormat with the required line spacing (again, this is your existing code):
// get the DirectWrite factory used by the font-wrapper
IDWriteFactory *pDWriteFactory;
hResult = fontWrapper->GetDWriteFactory(&pDWriteFactory);
// create an IDWriteTextFormat and set line spacing
IDWriteTextFormat *pTextFormat;
hResult = pDWriteFactory->CreateTextFormat(L"Arial", NULL,
DWRITE_FONT_WEIGHT_NORMAL, DWRITE_FONT_STYLE_NORMAL,
DWRITE_FONT_STRETCH_NORMAL, 10.0f, L"", &pTextFormat);
pTextFormat->SetLineSpacing(DWRITE_LINE_SPACING_METHOD_UNIFORM, 100.f, 20.0f);
Next, create a IDWriteTextLayout for your string (using your variable names) and using the IDWriteTextFormat created above:
// create a DirectWrite text layout for the string
// using the above IDWriteTextFormat
IDWriteTextLayout *pTextLayout;
unsigned int stringLength = s2ws(content).size();
hResult = pDWriteFactory->CreateTextLayout(
s2ws(content).c_str(),
stringLength,
pTextFormat,
0.0f,
0.0f,
&pTextLayout);
Set the font size in the IDWriteTextLayout object:
// set the required font size
DWRITE_TEXT_RANGE allText = {0, stringLength};
pTextLayout->SetFontSize(fontSize, allText);
And finally, draw the text using DrawTextLayout (again, using your variable names) :
// draw the text
fontWrapper->DrawTextLayout(
context,
pTextLayout,
startTextPosition.getX(),
startTextPosition.getX(),
color,
NULL,
NULL,
FW1_RESTORESTATE);
// tidy up interfaces
pTextLayout->Release();
pTextLayout = NULL;
I may have made some wrong assumptions from your existing code, but you can see how you can use your own IDWriteTextFormat via an IDWriteTextLayout instance and then use DrawTextLayout instead of DrawString. I hope this helps.