keywords: [UE4]PlayerController API In Common

获取当前的Pawn

一个Controller（包括AIController）只能同时possess一个Pawn。所以GetPawn()返回的就是当前控制的Pawn：

APawn* Pawn = PC->GetPawn();
Screen相关
//Convert 2D screen position to World Space 3D position and direction. Returns false if unable to determine value.
bool DeprojectScreenPositionToWorld(float ScreenX, float ScreenY, FVector& WorldLocation, FVector& WorldDirection) const;

/** Returns hit results from doing a collision query at a certain location on the screen */
bool GetHitResultAtScreenPosition(const FVector2D ScreenPosition, const ECollisionChannel TraceChannel, const FCollisionQueryParams& CollisionQueryParams, FHitResult& HitResult) const;

/**
 * Returns the PlayerState associated with the player at the specified index.
 * @param    PlayerIndex        the index [into the local player's GamePlayers array] for the player PlayerState to find
 * @return    the PlayerState associated with the player at the specified index, or None if the player is not a split-screen player or
 *            the index was out of range.
 */
class APlayerState* GetSplitscreenPlayerByIndex(int32 PlayerIndex = 1) const;


/**
 * After successful world to screen projection, allows custom post-processing of the resulting ScreenLocation.
 * @return Whether projected location remains valid.
 */
virtual bool PostProcessWorldToScreen(FVector WorldLocation, FVector2D& ScreenLocation, bool bPlayerViewportRelative) const;


/**
 * Convert a World Space 3D position into a 2D Screen Space position.
 * @return true if the world coordinate was successfully projected to the screen.
 */
bool ProjectWorldLocationToScreen(FVector WorldLocation, FVector2D& ScreenLocation, bool bPlayerViewportRelative = false) const;
鼠标光标固定位置不动

假设需求如下：
右键按住不放，屏幕转向，隐藏鼠标光标，松开右键时再显示鼠标光标，且鼠标光标的位置固定，不要跟随鼠标滑动而移动；
左键按住不放，光标显示，且光标跟谁鼠标滑动而移动（比如RTS的框选操作）。

解决方案如下：

void AMyPlayerController::OnLeftMousePressed()
{
    //由于光标默认捕获规则是：Viewport中鼠标任意键的按下事件就会永久捕获。
    //FInputModeGameAndUI默认规则是：捕获时隐藏光标。所以这里需要修改捕获时不隐藏光标，否则按住左键不放时光标会一直隐藏。
    FInputModeGameAndUI InputMode;
    InputMode.SetHideCursorDuringCapture(false);
    
    SetInputMode(InputMode);
}

void AMyPlayerController::OnLeftMouseReleased()
{
    //左键松开事件中不用做任何处理
}

void AMyPlayerController::OnRightMousePressed()
{
    //PlayerController的变量，控制是否隐藏光标
    bShowMouseCursor = false;
    
    //自定义变量，用来标识是否按住右键
    bRightMouseHold = true;

    SetInputMode(FInputModeGameOnly());
}

void AMyPlayerController::OnRightMouseReleased()
{
    bShowMouseCursor = true;
    
    bRightMouseHold = false;

    SetInputMode(FInputModeGameAndUI());
}

修改光标的捕获规则模式：
Project Settings -> Engine -> Input -> Viewport Properties -> Default Viewport Mouse Capture Mode.
默认是： Capture Permanently Including Initial Mouse Down，表示鼠标任意键的按下事件捕获，且是永久捕获。

How to show the mouse cursor at runtime

Code:

APlayerController* PC = GetController();
if (PC)
{
    PC->bShowMouseCursor = true; 
    PC->bEnableClickEvents = true; 
    PC->bEnableMouseOverEvents = true;
}

Reference
https://forums.unrealengine.com/development-discussion/c-gameplay-programming/47971-how-to-show-the-mouse-cursor-at-runtime-in-c

How to get Viewport size
void APlayerController::GetViewportSize(int32& SizeX, int32& SizeY) const;