add keyboard, fix display of negative numbers

qt_gui/main.cpp

@@ -19,6 +19,7 @@ int main(int argc, char** argv)
 	//fixed-width font for LCD
 	QFont fixedFont = QFontDatabase::systemFont(QFontDatabase::FixedFont);
 	fixedFont.setStyleHint(QFont::TypeWriter);
+	fixedFont.setPointSize(24);
 	engine.rootContext()->setContextProperty("_fixedFont", fixedFont);
 
 	//handle quit

qt_gui/main.qml

@@ -59,7 +59,7 @@ ApplicationWindow
 						color: "gray"
 						border { width: 1; color: "black" }
 						Text {
-							text: index
+							text: {getText(parent.parent.objectName, index)}
 							anchors.centerIn: parent
 						}
 						MouseArea {
@@ -71,4 +71,16 @@ ApplicationWindow
 			}
 		}
 	}
+
+	function getText(row, col) {
+		var keys = [
+			["Shift", "x<->y", "+/-", "C"],
+			["7", "8", "9", "/"],
+			["4", "5", "6", "*"],
+			["1", "2", "3", "-"],
+			["0", ".", "Enter", "+"]
+		]
+
+		return keys[row][col]
+	}
 }

src/lcd_emulator.c

@@ -76,7 +76,7 @@ static int is_valid_character(char letter){
 		return 1;
 	} else if(letter == CGRAM_EXP || letter == CGRAM_EXP_NEG){
 		return 1;
-	} else if(letter == '.' || letter == ' '){
+	} else if(letter == '.' || letter == ' ' || letter == '-'){
 		return 1;
 	}