QGridLayout, 3 panes, not expanding properly

Question

I'm trying to layout a window (all in code) with a QGridLayout. I can add widgets to the layout and they display in my window, but I can't figure out how to resize them properly. Here's what I'd like

[Leftmost][--------Center---------][Rightmost]

Those are the 3 "panes" of my window (all three of them lists). The left and right ones should be of a static width and hug their respective sides, and the center should expand to fill the width as the window grows (or shrinks).

Some code:

// Create the subviews, add them to a grid layout, and set the layout to the window.
QTableView *list = new QTableView(0);
list->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
QTableView *flashList = new QTableView(0);
flashList->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

QPushButton *infoButton = new QPushButton("Info!");
QPushButton *flashFeedsButton = new QPushButton("Flashfeeds");

QGridLayout *gridLayout = new QGridLayout;



// Set the minimum widths for all three columns of the grid
gridLayout->setColumnMinimumWidth(GridColumnFirst, 300);
gridLayout->setColumnMinimumWidth(GridColumnSecond, 300);
gridLayout->setColumnMinimumWidth(GridColumnThird, 300);

// Set the minimum heights for all rows of the grid
int headerFooterHeight = 44;
gridLayout->setRowMinimumHeight(GridRowFirst, headerFooterHeight);
gridLayout->setRowMinimumHeight(GridRowSecond, 200);
gridLayout->setRowMinimumHeight(GridRowThird, headerFooterHeight);


// Set the stretch factors
gridLayout->setColumnStretch(GridColumnFirst, 1);
gridLayout->setColumnStretch(GridColumnFirst, 2);
gridLayout->setColumnStretch(GridColumnThird, 1);

gridLayout->addWidget(list, 1, 0, Qt::AlignLeft);
gridLayout->addWidget(flashList, 1, 1, Qt::AlignCenter);
gridLayout->addWidget(infoButton, 0, 3, Qt::AlignRight);
gridLayout->addWidget(flashFeedsButton, 0, 1, Qt::AlignLeft);

_mainWindow->setLayout(gridLayout);

(As you might be able to tell, this is going to eventually be a 9x9 grid, but the point remains, I'm trying to get my middle row (GridRowSecond) to have the stretchy columns).

The rows themselves expand just fine. The problem seems to be getting the widgets at each cell to expand to take up their containing space. How do I do this? (also, vertically, my list is expanding properly, but not horizontally).

Answer 1

Look at the docs on QGridLayout::AddWidget:

The default alignment is 0, which means that the widget fills the entire cell.

But you have the following:

gridLayout->addWidget(list, 1, 0, Qt::AlignLeft);
gridLayout->addWidget(flashList, 1, 1, Qt::AlignCenter);
gridLayout->addWidget(infoButton, 0, 3, Qt::AlignRight);
gridLayout->addWidget(flashFeedsButton, 0, 1, Qt::AlignLeft);

Thus, you've specifically told the grid layout that you want your widget aligned to the left, center, right, and left of their cells, respectively. In your case you probably want to use the default alignment allowing the widgets to fill the cells and follow their own respective size policies.