I am learning DX9 and C++. I am making a pong game using Direct3D. I am trying to move the player paddle using the move_player variable in WMKEYDOWN and wParam==VKUP. I think I am having a scoping problem. Here is some of my code.

float move_player = 0.0f;

// this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_DESTROY:
	{
		PostQuitMessage(0);
		return 0;
	}

	case WM_KEYDOWN:
	{
		if (wParam == VK_UP)
		{
			move_player -= 50.0f;
			break;
		}
		else if (wParam == VK_DOWN)
		{
			move_player++;
			break;
		}
		break;
	}
	break;
	}
	return DefWindowProc(hWnd, message, wParam, lParam);
}

void init_graphics(void)
{
	// create the vertices using the CUSTOMVERTEX struct
	CUSTOMVERTEX vertices[] =
	{
		{ 0.0f, 250.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0), },
		{ 30.0f, 250.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0), },
		{ 0.0f, 350.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0), },
		{ 30.0f, 350.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0), },
	
		{ 770.0f, 250.0f + move_player, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255), },
		{ 800.0f, 250.0f + move_player, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255), },
		{ 770.0f, 350.0f + move_player, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255), },
		{ 800.0f, 350.0f + move_player, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255), },

		{ 390.0f, 290.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 255, 255), },
		{ 410.0f, 290.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 255, 255), },
		{ 390.0f, 310.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 255, 255), },
		{ 410.0f, 310.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 255, 255), },

	};

	// create a vertex buffer interface called v_buffer
	d3ddev->CreateVertexBuffer(12 * sizeof(CUSTOMVERTEX),
		0,
		CUSTOMFVF,
		D3DPOOL_MANAGED,
		&v_buffer,
		NULL);

	VOID* pVoid;    // a void pointer

	// lock v_buffer and load the vertices into it
	v_buffer->Lock(0, 0, (void**)&pVoid, 0);
	memcpy(pVoid, vertices, sizeof(vertices));
	v_buffer->Unlock();
}

if (wParam == VK_UP)
		{
			move_player -= 50.0f;
			break;
		}
		else if (wParam == VK_DOWN)
		{
			move_player++;
			break;
		}

Updating positions from message handling is tightly coupled but correct. However, in this case:

• If “up” moves the paddle 50 units and “down” 1 unit there's probably a mistake.
• You don't use move_player at all after updating its value.

He states that he thinks the “problem” is related to scoping but never says what the problem is, other than a vague reference to moving the paddle.

I guess people will start taking turns figuring out a solution to the unstated problem.

Maybe we can keep bumping this with “solutions” every time it scrolls off the front page.

It's Pong so there's no scoping issue. Maybe Lorenzo's comment will help Phil with the real problem.

Tom Sloper said:

It's Pong so there's no scoping issue. Maybe Lorenzo's comment will help Phil with the real problem.

What is the real problem Tom?

fleabay said:

What is the real problem Tom?

Unnecessary commentary. Let's see how it goes.

@LorenzoGatti can you go into more depth on your answer?

And we're done. Lorenzo's answer does not need explaining.