Having trouble moving a reticle around the screen while following Chili's Beginning DirectX tutorial - visual-c++

Question

To begin with I am using the Chili Framework for lessons 1-15 as downloadable here:
http://www.planetchili.net/
I am using DirectX 9 on an old laptop running Windows XP SP3. I have set the Direct3D rendering to software in order to run the framework. I am using Visual Studio Express C++ 2010 with the first service pack installed.
This is the code I am having trouble with:
// Start moving reticle code
DrawReticle(itemLocX, itemLocY, 255, 255, 255);
if(itemLocX == pointA && itemLocX != pointAb)
{
itemLocX += 2;
}
else if(itemLocX == pointBc && itemLocX != pointDa)
{
itemLocX -= 2;
}
if(itemLocY == pointAb && itemLocY != pointBc)
{
itemLocY += 2;
}
else if(itemLocY == pointDa && itemLocX != pointA)
{
itemLocY -= 2;
}
// End moving reticle code
Now Chili's solution is to move along the y axis while checking for x, and x while checking for y. I may post that later, don't have it readily available. You can see it at the beginning of this video:
http://youtu.be/JEmwkQsi8l0
However I wanted to do this logically, as if I was walking the border along an invisible wall inside a box. I wanted it to make sense what was going on. But the cursor won't move, and I see no reason why it doesn't. Here is my game.h:
#pragma once
#include "D3DGraphics.h"
#include "Keyboard.h"
class Game
{
public:
Game( HWND hWnd,const KeyboardServer& kServer );
void Go();
private:
void ComposeFrame();
/********************************/
/* User Functions */
void DrawReticle(int xP, int yP, int cR, int cG, int cB);
/*
xP = x position,
yP = y position,
cR = color red,
cG = color green,
cB = color blue
*/
// TODO: User functions go here
/********************************/
private:
D3DGraphics gfx;
KeyboardClient kbd;
/********************************/
/* User Variables */
int pointA; // Starting at pointA (100, 100) - the top left
int pointAb; // Move from pointA to pointAb (700, 100) - the top right
int pointBc; // Move from pointAb to pointBc (700, 500) - the bottom right
int pointCd; // Move from pointBc to pointCd (100,500) - the bottom left
int pointDa; // Move from pointCd to pointDa (100,100) - the top left
/*
These points describe the process of starting, then four movements. The four points are A, B, C, D. We start at A, then go to B (pointAb, read as A to b), then go to C (pointBc, read as B to c), then go to D (pointCd, read as C to d) then go to A (pointDa, read as D to a).
This can be very confusing, because there are five varibles used. But if we drew it out there would only four points, as well as only four movements. The best way to think of it is that starting is itself a movement, and as you need a place to start from, it itself must have a point. Since you start at A, but haven't yet gone anywhere, pointA is our starting point. Once you start moving, you go from pointA to pointB. Now if we used pointB as our variable it would be confusing,because we would have to move from pointA to pointB to pointC to pointD and then back to pointA. Still five variables, one is repeating, but the first pointA describes where you start, and the last where you end. Since these are two different actions on the same point, I have elected to use two letter names for each of the points you move to, while the point you start at has a single letter name. It was the best way I could clearly think about this process.
*/
int itemLocX; // Initial position of item on the x axis
int itemLocY; // Initial position of item on the y axis
int reticleX; // Initial position of reticle on the x axis
int reticleY; // Initial position of reticle on the y axis
// TODO: User variables go here
/********************************/
};
Here is my game.cpp:
#include "Game.h"
Game::Game( HWND hWnd,const KeyboardServer& kServer )
: gfx(hWnd),
kbd(kServer),
itemLocX(100), // Initial position of item on the x axis
itemLocY(100), // Initial position of item on the y axis
reticleX(400), // Initial position of reticle on the x axis
reticleY(300), // Initial position of reticle on the y axis
pointA(100), // Movement from 0 to A, stopping at A
pointAb(700), // Movement from A to b, stopping at B
pointBc(500), // Movement from B to c, stopping at C
pointCd(700), // Movement from C to d, stopping at D
pointDa(500) // Movement from D to a, stopping at A
{}
void Game::Go()
{
gfx.BeginFrame();
ComposeFrame();
gfx.EndFrame();
}
void Game::DrawReticle(int xP, int yP, int cR, int cG, int cB)
/*
xP = x position,
yP = y position,
cR = color red,
cG = color green,
cB = color blue
*/
{
gfx.PutPixel(xP-5,yP,cR,cG,cB);
gfx.PutPixel(xP-4,yP,cR,cG,cB);
gfx.PutPixel(xP-3,yP,cR,cG,cB);
gfx.PutPixel(xP+3,yP,cR,cG,cB);
gfx.PutPixel(xP+4,yP,cR,cG,cB);
gfx.PutPixel(xP+5,yP,cR,cG,cB);
gfx.PutPixel(xP,yP,cR,cG,cB);
gfx.PutPixel(xP,yP-5,cR,cG,cB);
gfx.PutPixel(xP,yP-4,cR,cG,cB);
gfx.PutPixel(xP,yP-3,cR,cG,cB);
gfx.PutPixel(xP,yP+3,cR,cG,cB);
gfx.PutPixel(xP,yP+4,cR,cG,cB);
gfx.PutPixel(xP,yP+5,cR,cG,cB);
}
void Game::ComposeFrame()
{
// Start draw reticle code
DrawReticle(reticleX, reticleY, 100, 155, 255);
// End draw reticle code
// Start color change code
int yT = 200; // Border 200 pixels from top
int yB = 400; // Border 200 pixels from bottom
int xL = 300; // Border 200 pixels from left
int xR = 500; // Border 200 pixels from right
if(reticleX < xL || reticleX > xR) // Defining color change area for X
{
DrawReticle(reticleX, reticleY, 255, 255, 255);
}
if(reticleY < yT || reticleY > yB) // Defining color change area for Y
{
DrawReticle(reticleX, reticleY, 255, 255, 255);
}
// End color change code
// Start moving reticle code
DrawReticle(itemLocX, itemLocY, 255, 255, 255);
if(itemLocX == pointA && itemLocX != pointAb)
{
itemLocX += 2;
}
else if(itemLocX == pointBc && itemLocX != pointDa)
{
itemLocX -= 2;
}
if(itemLocY == pointAb && itemLocY != pointBc)
{
itemLocY += 2;
}
else if(itemLocY == pointDa && itemLocX != pointA)
{
itemLocY -= 2;
}
// End moving reticle code
// Start border code
if(reticleX < 6)
{
reticleX = 6;
}
else if(reticleX > 794)
{
reticleX = 794;
}
if(reticleY < 6)
{
reticleY = 6;
}
else if(reticleY > 594)
{
reticleY = 594;
}
// End border code
// Start speed change code
int cSpeed = 4; // Default cursor speed
if(kbd.EnterIsPressed()) // Change to high speed
{
cSpeed = 8;
}
if(kbd.SpaceIsPressed()) // Change to low speed
{
cSpeed = 1;
}
if(kbd.RightIsPressed())
{
reticleX += cSpeed;
}
if(kbd.LeftIsPressed())
{
reticleX -= cSpeed;
}
if(kbd.UpIsPressed())
{
reticleY -= cSpeed;
}
if(kbd.DownIsPressed())
{
reticleY += cSpeed;
}
// End speed change code
}
Now I should note here that this should be done without functions and only the basic C++ operators. That's as far as Chili has taught to this point. This is my second attempt to solve this myself, after hours thinking about it and working on it on paper. I'm stuck. Just not seeing it. I think there is a logic error here on my part. I want to understand where my thinking may be mistaken, but more than that, how to think correctly, like the computer, about this.
I am also open to advice regarding my coding style. If I am not being clear enough, or am doing something that should not become a bad habit - basically if there is something I should be doing differently in writing my code I would like to know about it.
Thank you for your help - it is very much appreciated!

Answer 1

I see how you have tried to do this. Personally you have over complexed it.
1: you don't need the != operator in your if statements.
2: try this:
if(itemLocX < 700)
{
itemLocX += 2;
}
3: This worked fine during testing. Another point is that the if statements could be in the wrong order. I changed it to the order in which it moved across the screen in. I have X Y X Y and you have X X Y Y. (unconfirmed) It executes the if statements in order. I have hard coded the answer. set them to variables if you really want to. Hope this helped!